The Helicidae are the most noteworthy of the San Domingo land Mollusca. The group Eurycratera, which contains some of the finest existing land snails, is quite peculiar, while Parthena, Cepolis, Plagioptycha, and Caracolus here reach their maximum. The Cylindrellidae are very abundant, but no section is peculiar. Land operculates do not bear quite the same proportion to the Pulmonata as in Cuba and Jamaica, but they are well represented (100 to 152); Rolleia is the only peculiar genus.
The relations of San Domingo to the neighbouring islands are considerably obscured by the fact that they are well known, while San Domingo is comparatively little explored. To this may perhaps be due the curious fact that there are actually more species common to Cuba and Porto Rico (26) than to Porto Rico and San Domingo. Cuba shares with San Domingo its small-sized Caracolus and also Liguus, but the great Eurycratera, Parthena, and Plagioptycha are wholly wanting in Cuba. The land operculates are partly related to Cuba, partly to Jamaica, thus Choanopoma, Ctenopoma, Cistula, Tudora, and many others, are represented on all these islands, while the Jamaican Stoastoma occurs on San Domingo and Porto Rico, but not on Cuba, and Lucidella is common to San Domingo and Jamaica alone. An especial link between Jamaica and San Domingo is the occurrence in the south-west district of the latter island of Sagda (2 sp.). The relative numbers of the genera Strophia, Macroceramus, and Helicina, as given below (p. [351]), are of interest in this connexion.
Porto Rico, with Vièque, is practically a fragment of San Domingo. The points of close relationship are the occurrence of Caracolus, Cepolis, and Parthena among the Helicidae, and of Simpulopsis, Pseudobalea, and Stoastoma. Cylindrella and Macroceramus are but poorly represented, but Strophia still occurs. The land operculates (see the Table) show equal signs of removal from the headquarters of development. Megalomastoma, however, has some striking forms. The appearance of a single Clausilia, whose nearest relations are in the northern Andes, is very remarkable. Gaeotis, which is allied to Peltella (Ecuador only), is peculiar.
Fig. 231.—Examples of West Indian Helices: A, Helix (Parthena) angulata Fér., Porto Rico; B, Helix (Thelidomus) lima Fér., Vièque; C, Helix (Dentellaria) nux denticulata Chem., Martinique.
Land Mollusca of the Greater Antilles
| Cuba. | Jamaica. | S. Domingo. | Porto Rico. | |
| Glandina | 18 | 24 | 15 | 8 |
| Streptostyla | 4 | ... | 2 | ... |
| Volutaxis | ... | 11 (?) | 1 | ... |
| Selenites | 1 | ... | ... | ... |
| Hyalinia | 4 | 11 | 5 | 6 |
| Patula | 5 | 1 | ... | ... |
| Sagda | ... | 13 | 2 | ... |
| Microphysa | 7 | 18 | 8 | 3 |
| Cysticopsis | 9 | 6 | ... | ... |
| Hygromia (?) | ... | ... | 3 | ... |
| Leptaxis (?) | ... | ... | 1 | ... |
| Polygyra | 2 | ... | ... | ... |
| Jeanerettia | 6 | ... | ... | 1 |
| Euclasta | ... | ... | ... | 4 |
| Plagioptycha | ... | ... | 14 | 2 |
| Strobila | ... | 1 | ... | ... |
| Dialeuca | ... | 1 | ... | ... |
| Leptoloma | 1 | 8 | ... | ... |
| Eurycampta | 4 | ... | ... | ... |
| Coryda | 7 | ... | ... | ... |
| Thelidomus | 15 | 3 | ... | 3 |
| Eurycratera | ... | ... | 7 | ... |
| Parthena | ... | ... | 2 | 2 |
| Cepolis | ... | ... | 3 | 1 |
| Caracolus | 8 | ... | 6 | 2 |
| Polydontes | 3 | ... | ... | 1 |
| Hemitrochus | 12 | 1 | ... | ... |
| Polymita | 5 | ... | ... | ... |
| Pleurodonta | ... | 34 | ... | ... |
| Inc. sed. | 5 | ... | ... | ... |
| Simpulopsis | ... | ... | 1 | 1 |
| Bulimulus | 3 | 3 | 6 | 7 |
| Orthalicus | 1 | 1 | ... | ... |
| Liguus | 3 | ... | 1 | ... |
| Gaeotis | ... | ... | ... | 3 |
| Pineria | 2 | ... | ... | 1 |
| Macroceramus | 34 | 2 | 14 | 3 |
| Leia | ... | 14 | 2 | ... |
| Cylindrella | 130 | 36 | 35 | 3 |
| Pseudobalea | 2 | ... | 1 | 1 |
| Stenogyra | 6 | 7 | (?) | ... |
| Opeas | 8 | (?) | 4 | 6 |
| Subulima | 6 | 14 | 2 | 2 |
| Glandinella | 1 | ... | ... | ... |
| Spiraxis | 2 | (?) | 2 | 1 |
| Melaniella | 7 | ... | ... | ... |
| Geostilbia | 1 | ... | 1 | ... |
| Cionella | 2 | ... | ... | ... |
| Leptinaria | ... | 1 | ... | 3 |
| Obeliscus | ... | ... | 1 | 2 |
| Pupa | 2 | 7 | 3 | 2 |
| Vertigo | 4 | ... | ... | ... |
| Strophia | 19 | ... | 3 | 2 |
| Clausilia | ... | ... | ... | 1 |
| Succinea | 11 | 2 | 5 | 3 |
| Vaginula | 2 | 2 | 2 | 1 |
| Megalomastoma | 13 | ... | 1 | 3 |
| Neocyclotus | 1 | 33(?) | ... | ... |
| Licina | 1 | ... | 3 | ... |
| Jamaicia | ... | 2 | ... | ... |
| Crocidopoma | ... | 1 | 3 | ... |
| Rolleia | ... | ... | 1 | ... |
| Choanopoma | 25 | 12 | 19 | 3 |
| Ctenopoma | 30 | 2 | 1 | ... |
| Cistula | 15 | 3 | 3 | 3 |
| Chondropoma | 57 | (?) | 19 | 4 |
| Tudora | 7 | 17 | 5 | ... |
| Adamsiella | 1 | 12 | ... | ... |
| Blaesospira | 1 | ... | ... | ... |
| Xenopoma | 1 | ... | ... | ... |
| Cistula | 15 | 3 | 3 | ... |
| Colobostylus | 4 | 13 | 5 | ... |
| Diplopoma | 1 | ... | ... | ... |
| Geomelania | ... | 21 | ... | ... |
| Chittya | ... | 1 | ... | ... |
| Blandiella | ... | ... | 1 | ... |
| Stoastoma | ... | 80 | 1 | 1 |
| Eutrochatella | 21 | 6 | 6 | ... |
| Lucidella | ... | 4 | 1 | ... |
| Alcadia | 9 | 14 | 4 | ... |
| Helicina | 58 | 16 | 24 | 9 |
| Proserpina | 2 | 4 | ... | ... |
The Virgin Is., with St. Croix, Anguilla, and the St. Bartholomew group (all of which are non-volcanic islands), are related to Porto Rico, while Guadeloupe and all the islands to the south, up to Grenada (all of which are volcanic), show marked traces of S. American influence. St. Kitt’s, Antigua, and Montserrat may be regarded as intermediate between the two groups. St. Thomas, St. John, and Tortola have each one Plagioptycha and one Thelidomus, while St. Croix has two sub-fossil Caracolus which are now living in Porto Rico, together with one Plagioptycha and one Thelidomus (sub-fossil). The gradual disappearance of some of the characteristic greater Antillean forms, and the appearance of S. American forms in the Lesser Antilles, is shown by the following table:—
| S | ||||||||||||||||
| P | S | S | G | M | t | |||||||||||
| o | t | S | t | u | a | S | . | |||||||||
| r | . | t | A | . | a | D | r | t | B | T | ||||||
| t | S | . | T | n | A | d | o | t | . | a | V | G | r | |||
| o | T | t | o | g | K | n | e | m | i | r | i | r | i | |||
| h | . | C | r | u | i | t | l | i | n | L | b | n | e | n | ||
| R | o | r | t | i | t | i | o | n | i | u | a | c | n | i | ||
| i | m | J | o | o | l | t | g | u | i | q | c | d | e | a | d | |
| c | a | a | i | l | l | ’ | u | p | c | u | i | o | n | d | a | |
| o | s | n | x | a | a | s | a | e | a | e | a | s | t | a | d | |
| . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | . | |
| Bulimulus | 7 | 4 | 2 | 4 | 1 | 2 | 2 | 3 | 8 | 9 | 5 | 3 | 3 | 6 | 2 | 4 |
| Cylindrella | 3 | 2 | 1 | 1 | 1 | . | . | . | . | 1 | 1 | 1 | 1 | . | . | 1 |
| Macroceramus | 3 | 1 | 1 | . | 2 | 1 | . | . | . | . | . | . | . | . | . | . |
| Cyclostomatidae, etc. | 23 | 4 | 1 | 5 | 1 | 1 | 1 | . | 4 | . | . | . | . | . | . | 1 |
| Dentellaria | . | . | . | . | . | . | 1 | 1 | 8 | 5 | 11 | 2 | 2 | . | 1 | 1 |
| Cyclophorus | . | . | . | . | . | . | . | . | 1 | 2 | 2 | . | . | . | . | . |
| Amphibulimus | . | . | . | . | . | . | . | . | 2 | 3 | 1 | . | . | . | . | . |
| Homalonyx | . | . | . | . | . | . | . | . | 1 | 1 | . | . | . | . | . | . |
(d) In Guadeloupe we find Cyclophorus, Amphibulimus, Homalonyx, and Pellicula, which are characteristic of S. America, and nearly all recur in Dominica and Martinique. These islands are the metropolis of Dentellaria, a group of Helix, evidently related to some of the forms developed in the Greater Antilles. Stragglers occur as far north as St. Kitt’s and Antigua, and there are several on the mainland as far south as Cayenne. Traces of the great Bulimus, so characteristic of South America, occur as far north as S. Lucia, where also is found a Parthena (San Domingo and Porto Rico). Trinidad is markedly S. American; 55 species in all are known, of which 22 are peculiar, 28 are common to S. America (8 of these reach no farther north along the islands), and only 5 are common to the Antilles, but not to S. America. The occurrence of Gundlachia in Trinidad has already been mentioned.