_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.