ON SPLANCHNOTROPHUS. 51 
Kroyer's genus Selivs; while a similarly well-developed abdomen is to be found in 
Tucca impressa. 
The most remarkable characteristic, however, of this genus is to be found in the 
degree of development of the thorax of the male. Posterior to the two pair of foot-jaws, 
and, like them, attached to the first cephalothoracie segment, we find two pairs of feet, 
the representative appendages of two thoracic segments; and posterior again to these, 
and between them and the first abdominal or genital segment, there are three distinct 
segments, and these constitute therefore the third, fourth, and fifth of the thorax. We 
search in vain throughout the whole order of the Peecilopoda for an analogous instance 
of thoracic development. Even among the Caligidze, where we meet with four pairs of 
thoracic appendages, the representative of the fifth segment cannot be distinguished, 
since that segment which is the seat of the external generative organs, from which 
issue the ovigerous sacs, and which has been regarded by Milne-Edwards and other 
authors as the last thoracic, is not so, but the first or, according to Dana, the equiva- 
lent of the first and second abdominal segments. 
SPLANCHNOTROPHUS GRACILIS, n.s. (Pl. XV. & Pl. XVI. figs. 7-10.) 
Parasite of Doris pilosa, Alder and Hancock, Brit. Nud. Moll. p. 26, pl. 45. figs. 6-9. 
In feminis cephalothorax elongatus, gracilis. Appendices thoracice utrinque tres, lon- 
gissimz, maxime attenuate, toto corpore longiores dimidio. Pedes biramei (ramus 
unus perbrevis), articulati; ungues graciles. Annulus genitalis lageniformis, cepha- 
lothorace angustior, postice dilatatus, bilobatus. Appendices caudales minute, stilo 
uno non plumoso instructee. 
Long. vix 1 uncis; lat. (appendicibus lateralibus computatis) $ uncis. 
In maribus cephalothorax quadriarticulatus; annulus primus oblongus, pedum duobus 
paribus at non appendicibus lateralibus instructus; annulus secundus, tertius quartus- 
que ejusdem latitudinis primoque segmento multo angustiores. Abdomen capitisque 
membra iisdem feminz similia. 
Long. 4l; unc. ; lat. gy unc. 
Sub pelle tectus Doridis pilose et Idalie asperse visceribus vescitur. 
The Female. 
The body is elongated, slightly depressed, of nearly equal diameter throughout, and 
covered with a tough though yielding membrane. The cephalothorax, which occupies 
by far the greatest portion of the body, is produced at the sides into three pairs of lateral 
processes, placed a little apart from each other. These processes (Pl. XV. fig.1 b) are 
inarticulate, soft, and cylindrical, very long and slender, being fully half as long again as 
the total length of the body, and gradually taper to fine points. The head, though 
blended with, is somewhat narrower than the thorax, and projects a little forwards. The 
posterior extremity of the thorax is prolonged backwards beyond the origm of the last 
pair of thoracic processes. The sides of this portion are concave (Pl. XV. fig. 2 a); and it 
is produced behind into two obtuse lateral lobes, and in some instances has the appear- 
ance of forming a distinct segment—a depressed line dividing it from the per at the 
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MISSOTIRI 
