ON SPLANCHNOTROPHUS. 53 
second segment is quite rudimentary, but suffices to give support to two extremely 
minute caudal appendages, each of which has a short terminal seta. 
The ovigerous sacs have not been seen entire; but in most instances the remains of 
them were found adhering to the sides of the first abdominal segment, and in some cases 
they contained a few eggs of a yellow colour. The sacs were of an elongated-oval form, 
and the eggs agglomerated within, —an arrangement which appears to be as universal in 
the family of Chondracanthidz as is the disposition of the ova in single file among the 
Caligidee. 
Length of the body nearly a quarter of an inch; breadth, from tip to tip of the lateral 
processes, upwards of three-quarters of an inch. 
The Male. 
The cephalothorax in the male (Pl. XV. figs. 7, 8) is composed of four articulations. 
The first of these is very large as compared with the rest, subquadrilateral in form, and 
having the posterior angles well rounded. The cephalic portion is narrower than the 
thoracic, and projects considerably forward. It is somewhat squared in front, and bears 
a single eye near the centre. The first antennse (Pl. XVI. fig. 7) are similar to those of 
the female, except that there is a strong seta on the outer margin of the second or third, 
and several of less size on the terminal joint. The second antennz and organs of the 
mouth (Pl. XV. fig. 9) are likewise similar to those of the female. The male, too, has two 
pairs of thoracic feet, which in position and character agree with the same organs in the 
other sex, only that they are relatively larger, and the second or rudimentary branch 
springing from the basal joint is more largely developed (Pl. XV. fig. 10 @), and the 
minute spines on the second and third joints have not been observed. The second, 
third, and fourth segments, in consequence of their greatly diminished size as compared 
with the first, both in length and breadth, and their close agreement in these respects 
with the segments posterior to them, might readily be mistaken for abdominal members, 
were it not that their position anterior to the genital segment clearly proves them to be 
thoracic. They are scarcely one-third the width of the first segment; the breadth of 
each slightly exceeds the length; and they are unprovided with appendages. : Taken 
together with the abdominal segments, they form, as it were, a gradually tapering tail, 
appended to the greatly developed anterior segment. 
The abdomen is two-jointed. On each side of the first of these segments, at its 
junction with the second, is seen a tubercular swelling, which is perforated, and through 
which a curved process—the male intromittent organ (Pl. XV. fig. 11 e)—is usually pro- 
truded. The last segment is small, tapers backwards, and supports two caudal processes, 
each of which terminates in a short, stoutish seta. 
Length of body {th of an inch; breadth of the same 3nd of an inch. TN 
Several females of this species have been obtained from specimens of dad pilosa, 
which had been taken on the Devonshire coast; and one has occurred in Idalia aspersa, 
from the West of Ireland. There is never more than one individual found in the same 
Nudibranch, and this invariably occupies the same position, resting upon the n 
surface of the liver-mass and embracing two-thirds of it with its long, attenuated late 
