50 MR. A. HANCOCK AND THE REV. A. M. NORMAN 
were infesting the Doto in rock-pools at Cullercoats; and it is chiefly from these speci- 
mens that the description of the species has been drawn up. 
These two animals are so unlike all known forms, that it is necessary to establish a 
new genus for their reception, which we propose thus to characterise :— 
Fam. CHONDRACANTHID. 
Genus SPLANCHNOTROPHUS *, n. g. 
Femine cephalothorax uni- vel bi-annulatus, appendicibus utrinque elongatis, simplicibus, cylindricis 
instructus. Antenne prime minute ; secundz majores, prehensiles. Maxillipedes cum mandi- 
bulis maxillisque juxta os positi. Pedum thoracicorum duo paria non natatoria, unguiculata. Ab- 
domen biannulatum ; annulus posterior appendicibus caudalibus stiligeris confectus. Ova externa, in 
sacculos ellipticos aggregata. - ; 
Mas perpusillus, a femina cephalothorace quadriannulato, appendicibus lateralibus carente differt. 
Species nobis cognitae Molluscorum Nudibranchiatorum viscera habitant. 
Female. Head and thorax either blended into a single segment, the thoracic portion of which is fur- 
nished on each 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, segment. In this 
case, however, all the thoracic appendages are attached to the first segment. First antennae minute and 
few-jointed ; second larger, in the form of prehensile hooks.  Labrum large, overhanging the mandibles, 
which organs, together with the maxillae 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 
setze. Ovigerous sacs elliptical. 
Male minute. Cephalothorax without lateral appendages, and divided into four segments, the first of 
which bears the two pairs of thoracic feet. ` 
The species which have as yet been discovered inhabit the bodies of Nudibranchiate Mollusca, lodged 
beneath the skin, and feeding on the viscera. 
The presence of true thoracic feet, and the extent of development of the abdomen in 
both sexes, and also the perfect segmentation of the thorax in the male, all point to the 
claim which Splanchnotrophus has to take its position at the head of the family to which 
we have assigned it. 
The genus shows affinity to many allies in the development of its several organs. ln 
the structure of the antenns, and the general arrangement of the parts about the 
mouth—in the deficiency of segmentation of the thorax of the female, and the atrophy 
of the posterior pairs of feet—in the character of the egg-sacs, and in the vast dispro- 
portion of size between the sexes, we find our authority for associating Splanchnotrophus 
with the Chondracanthidee. Again, in the presence of the curious produced appendages 
which take their origin from the sides of the thorax, we are reminded of Chondracanthus 
more especially, while the exact structure of the oral organs finds its nearest counter- 
part in the mouth of the male of that same genus, as will be more partieularly pointed 
out in the specific descriptions; the presence of ambulatory thoracic feet is paralleled in 
* exÀdyyxva, the viscera; rpéóew, to nourish. 
