SCYLL^A. 



into another. Here, however, the typical character of the Tritoniada is still sufficiently 

 preserved to allow of our retaining the genus in that family. This is the only nudibranchiate 

 mollusk in which any armature of the stomach, performing the functions of a gizzard, has been 

 detected. 



The body of Scyllaa is elongated, very much compressed at the sides, and gibbous upon the 

 back, sloping down to the anterior and posterior extremities. It has two tentacles, which are 

 dorsal, but placed forwards nearly above the head. They are rather small, clavate, and 

 laminated, and are retractile within large sheaths ; these are wide near the top, tapering to a 

 narrow base, and are stated to be very contractile : the orifice inclines forwards, and there is 

 a thin, arched, crest-like appendage behind it. The head is sub-inferior ; the mouth fleshy, 

 without oral tentacles, and covered by a slight velar expansion of the frontal margin. The 

 jaws are corneous. On each side of the back arise two or three erect flattened lobes of 

 irregular form. On the inside of these, as well as on the median portion of the back, are 

 placed the branchiae, which consist of small tufts of delicately branched filaments, disposed in 

 an irregular manner. The foot is linear and very narrow, with the sides thin and flexible, 

 formed for clasping the stems of sea-weeds. The anus is situated on the right side between 

 the first and second dorsal lobe, and nearly equally distant from the two extremities of the 

 body. The orifice of the generative organs is placed lower down and more forward on the 

 same side, being only a short distance behind the right tentacle. 



On opening the animal from above, the buccal mass is seen to occupy the anterior 

 extremity of the body. This organ is rather larger than usual, and is of an oblong ovate form, 

 narrowest in front. It is furnished with horny, cutting jaws, resembling those of JEolis. The 

 tongue, however, is formed after the type of Tritonia : its anterior portion is convex, and 

 assumes a sub-conical form, with the apex turned upwards and forwards ; posteriorly, it 

 becomes concave, the concavity being directed towards the oesophagus, and having the 

 appearance of a cylinder, capable of being turned inside out. The whole of this organ is 

 covered with denticulated spines, rising over the projecting part, and entering into the cavity: 

 they form about thirteen transverse rows, divided by a narrow groove down the centre, on 

 which, in each row, is a broad plate containing a central tooth, with three or four denticulations 

 on each side. The points of the spines are directed backwards and inwards, so that when the 

 tongue is advanced, and the margins of the concavity separated, it will become a powerful 

 prehensible apparatus, at once able to rasp down the food and carry it to the oesophagus. 



The oesophagus is long and rather wide, and shortly after leaving the buccal mass, is 

 surrounded for some little distance by a glandular layer of follicular organization, probably 

 salivary in its function : it then continues its course backwards, and, after dipping downwards, 

 bends upwards and empties itself into the posterior part of a small globular stomach, with the 

 ends somewhat flattened, situated on the left side of the body. The interior of this stomach 

 is lined with a broad transverse belt of dark, horny, lancet-formed plates, having their edges 

 and points sharp, and directed towards the centre of the cavity, which they almost fill. This 

 peculiar dental armature is well adapted to cut in pieces alimentary matters. 



A wide intestinal tube is given off from this organ, opposite to the entrance to the 

 oesophagus, which tube, running forwards a short way, arches across to the right side of the 

 body, immediately in front of the heart ; it then passes backwards in contact with the skin, 

 and terminates at the constricted anal orifice a little in advance of the second branchial lobe. 



