The Common Lobster is found on the coasts of Western Europe, from Norway to the Mediterranean, living in shallow water, generally a little way below low-tide mark, wherever a rough, rocky bottom affords suitable lurking-places. On the Atlantic coast of North America, Lobsters are also found abundantly in similar situations. These American Lobsters, if examined carefully, will be found to differ from the European kind in certain small details of structure, of which the most conspicuous is the presence, on the under-side of the rostrum, of two spines or teeth. In the European Lobsters the under-side of the rostrum is smooth ([Fig. 9]). In the nomenclature of technical zoology, these two kinds or species of Lobster are said to constitute (along with a third species found at the Cape of Good Hope) the genus Homarus, the European species being known as Homarus gammarus, and the American as Homarus americanus. The so-called "Norway Lobster" or "Dublin Prawn," which differs from the Common Lobster in having large kidney-shaped eyes and long and slender claws, and in many other details of structure, is placed in a distinct genus, and is known as Nephrops norvegicus. The genera Homarus and Nephrops, together with some others, constitute the family Homaridæ, which again is grouped with other families in a tribe, Nephropsidea, forming a part of the order Decapoda. These groups are intended to express the varying degrees of resemblance and difference in structure between the species of animals which make up the class Crustacea. Since we have good grounds for believing that all these species have arisen by some mode of evolution, this classification also represents the varying degrees of actual relationship between the different forms, so far as this relationship can be discovered. In the next chapter a brief sketch of the chief subdivisions of the Crustacea is given, with such details as to the characteristics of each as are necessary to render intelligible the succeeding chapters on their habits and modes of life.
[CHAPTER III]
THE CLASSIFICATION OF CRUSTACEA
Table of Classification of Crustacea
| Class CRUSTACEA. | |||||
| Subclass | Branchiopoda | - | { | Order | Anostraca. |
| { | " | Notostraca. | |||
| { | " | Conchostraca. | |||
| { | " | Cladocera. | |||
| " | Ostracoda | - | { | " | Myodocopa. |
| { | " | Podocopa. | |||
| " | Copepoda | - | { | " | Eucopepoda. |
| { | " | Branchiura. | |||
| " | Cirripedia | - | { | " | Thoracica. |
| { | " | Rhizocephala. | |||
| " | Malacostraca. | ||||
| Series | LEPTOSTRACA | - | " | Nebaliacea. | |
| " | EUMALACOSTRACA. | ||||
| Division | Syncarida | - | " | Anaspidacea. | |
| " | Peracarida | - | { | " | Mysidacea. |
| { | " | Cumacea. | |||
| { | " | Tanaidacea. | |||
| { | " | Isopoda. | |||
| { | " | Amphipoda. | |||
| " | Eucarida | - | { | " | Euphausiacea. |
| { | " | Decapoda. | |||
| " | Hoplocarida | - | { | " | Stomatopoda. |
Fig. 10—The "Fairy Shrimp" (Chirocephalus diaphanus), Male. × 2. (After Baird.)