In the mouth, the lower teeth of the mandibles are more distinct than in [V. Strömia]; the lower part of the edge of the maxilla is very prominent. In the second and third pairs of cirri the terminal spines on the shorter rami are coarsely pectinated; on the sixth pair there are only three pairs of main spines on each segment; but these several points, according to the analogy of other species, I should expect to be variable.
This species is alluded to by Bruguière, in the ‘Encyclopédie Méthodique,’ but was confounded by him with the [V. Strömia] of Europe.
3. [VERRUCA] SPENGLERI. Pl. [21], fig. [2].
Moveable scutum, with a sharp, straight, medial adductor ridge: fixed scutum not larger than the fixed tergum.
Hab.—Madeira, Mus. Lowe; attached to shells.
It would appear that the present species does not attain quite so large a size as the more northern [V. Strömia]; the walls are not longitudinally ribbed as is usual with this latter species. The proportional sizes of the compartments seem to be somewhat different; the fixed scutum is either equal to or even smaller than the fixed tergum, instead of being larger, as in [V. Strömia]; but in young individuals the proportions are reversed. In several specimens the fixed scutum and tergum together were larger than the carina. The rounded adductor plate of the fixed scutum is extremely large. The lines of growth, especially on the moveable opercular valves, are rather more plainly crenated than in [V. Strömia]. In the moveable scutum the lower articular ridge on the tergal margin varies a little in size, and is sometimes larger than in [V. Strömia] (but never so large as in [V. lævigata]), and is placed more in the middle of the tergal margin: but by far the most important character by which this species can be distinguished from all the others, is the presence, on the under side of the moveable scutum, of a straight, prominent adductor ridge, which runs up to and even under the apex of the valve, for it is there slightly hollowed out. In the moveable tergum, owing to the medial position of the lower articular ridge of the scutum, the middle of the scutal margin is more hollowed out, and the axial ridge narrower, than in [V. Strömia].
In the animal’s body the only difference which I could perceive was that the shorter rami of the second and third pairs of cirri were not so short, compared either to the other cirri or to the longer rami of these same cirri. In the second cirrus, in a moderately-sized specimen, the segments were six and thirteen in number in the two rami, and in the third cirrus, seven and fifteen.
Had it not been for the specimen in the British Museum of [V. Strömia], from the Red Sea, I should have concluded, from geographical considerations, that [V. Spengleri] probably was the species found in the Mediterranean, and noticed by Spengler (‘Schriften der Berl. Gesell.,’ 1 B., 1780), as a small variety of the northern [V. Strömia]; and likewise that it was the Creusia echinoides of Risso (‘Hist. Nat. Product. de l’Europe,’ tom. 4, p. 382, 1826), which is certainly a [Verruca], but not described with sufficient minuteness to be recognised.