MUSEUM OF COMPARATIVE ZOOLOGY. 399 



hind the head and foot, in the two specimens dissected, the soft parts were 

 totally decayed and lost, having probably been left too long out of alcohol in the 

 tropical temperature after the draughtsman had made his drawings. Nothing 

 remained of the gills, and only the anterior lobes of the mantle, the appearance 

 of which in life is preserved by the drawings made from the living animal. 



The cavity of the mouth is large, and the muscles which move the buccal 

 mass are prominent and strong. There are no functional mandibles; the 

 jaws, if such they may be called, are disproportionately small and weak. They 

 consist of two quadrate smooth horny pieces about 1.5 mm. square, meeting 

 above in the median line at the anterior upper portion of the oral cavity. 

 They are attached over their whole extent, flatly to the roof of the mouth, 

 have no cutting edge, in fact are too soft and weak to cut anything, and evi- 

 dently only serve the purpose of defending the surface to which they are fixed 

 from the attrition of the teeth of the radula below them. 



The radula is long and its central part is of a very dark red brown. There is 

 a narrow pointed rhachidian tooth, with a slightly curved simple tip. The 

 other teeth are arranged in three series. The laterals proper ars twenty-six in 

 number, and the line forms a very acute angle on each side of the rhachidian 

 tooth, which would occupy a position a little within the apex of this angle. 

 The largest laterals are those near the rhachidian tooth; they have simple broad 

 cusps and narrower bases; a faint midrib was visible on some of them near the 

 base. They grow gradually smaller and shorter from the centre outward, 

 though preserving a general similarity of form ; the outer five are without cusps, 

 and are little more than pointed lamellae. Outside of the laterals are two 

 series of uncini; the inner series or major uncini are large, strongly curved, 

 with scythe-shaped cusps, having from one to three denticles nearly as large as 

 the principal cusp. Those nearer the rhachis have more and the outer ones 

 have fewer denticles, the outer ones are also a little shorter and more slender. 

 As nearly as I could determine there were eighteen (possibly twenty) of these 

 uncini, their tips forming an arch raised above the median teeth and also above 

 the minor uncini. The successive rows in a general view of the radula look 

 like successive waves running in at an angle less oblique to the median line 

 than the teeth on the rhachis. The minor laterals form a very numerous se- 

 ries of decidedly smaller and more transparent teeth, which series, though really 

 inclined toward the median line at a very acute angle, appears parallel with it. 

 The uncini so overlap and confuse with one another as to make it impossible to 

 state witli confidence the exact number in a single transverse series; I believe 

 it to be more than forty, and probably less than fifty. They are slender, 

 spatulifonn, nearly straight transparent lamellae, whose weakness contrasts 

 strongly with the stout arched dentate broad-cusped major laterals. 



The major and minor laterals respectively are set in series on a compact 

 solid base, common to all of the teeth in that series belonging to one transverse 

 set, and not very clearly separated from the basis of adjoining sets. This adds 

 to the difficulty of obtaining the exact number in any one transverse set, where 

 the teeth are so numerous and so compactly planted. I did not observe on any 



