134 TRANSACTIONS OF THE LINNEAN SOCIETY. 
Both are internal parasites, lying buried within the visceral 
chamber of their victims. The minute caudal extremity, 
and the ovigerous sacs of the female, however, appear at the 
surface.” 
One species was obtained in Doris pilosa, from the coast 
of Devonshire, and has since also occurred in J/dalia aspersa, 
taken on the west coast of Ireland. The other species has been 
found in Eolis rufibranchialis and Doto coronata, captured on 
the shores of Northumberland. The characters of the genus 
Splanchnotrophus are thus given :— 
Female.—Head and thorax either blended into a single 
segment, the thoracic portion of which is furnished on either 
side with unarticulated arm-like appendages or lobes, or the 
first part only of the thorax is united with the head, and the 
last part forms a second but comparatively minute seg- 
ment. In this case, however, all the thoracic appendages 
are attached to the first segment. First antenne minute 
and few jointed; second larger, in the form of prehensile 
hooks. Labrum large, overhanging the mandibles, which 
organs, together with the maxille and two pairs of foot-jaws, 
are minute and crowded round the mouth. Thoracic feet 
two pairs, minute, simple, or two-branched, terminating in 
hooks. Abdomen two-jointed, the last joint ending in two 
caudal appendages, which are furnished with one or two 
simple sete. Ovigerous sacs elliptical. 
Male.—Minute. Cephalothorax without lateral append- 
ages, and divided into four segments, the first of which bears 
the two pairs of thoracic feet. 
The genus belongs to the family Chondracanthide, and 
its most remarkable characteristic, as pointed out by the 
authors, is the ‘‘ degree of development of the thorax in the 
male.’ Posterior to the two pair of foot-jaws, and, like them, 
attached to the cephalothoracic segment, we find two pairs 
of feet, the representative appendages of two thoracic seg- 
ments; and posterior again to these, and between them and 
the first abdominal or genital segment, there are three dis- 
tinct segments; and these constitute, therefore, the third, 
fourth, and fifth ofthe thorax. We search in vain throughout 
the whole order of the Peecilopoda for an analogous instance 
of thoracic development. 
Two species are then described, viz. :— 
1. Splanchnotrophus gracilis. In Doris pilosa and Idalia 
aspersa ; and 
2. S. brevipes, found in Doto coronata, and EH. rufibran- 
chials. 
Of the former species several females were obtained ; but 
