TRITONIIDAE. 5 



two measure 4 mm. across. The masticatory process is not long ; both it and the 

 edges of the jaws bear about five rows of denticles, the outermost very distinct. The 

 radula is mahogany brown, and has a formula of at most 32 x 30.1.1.1.30. The 

 median tooth is broad and tricuspid ; the central cusp strong and triangular at the top, 

 the side cusps rounder and more irregular. The first lateral is of the usual clumsy 

 shape ; the remaining laterals rather erect and bent at the tip. The salivary glands 

 are about 5 mm. long ; they look like smooth bands and are inconspicuously folliculate. 

 The oesophagus proper is very short, and almost immediately after issuing from the 

 buccal mass begins to dilate into a pouch which becomes the stomach, though it is hard 

 to say at what points distinct names should be applied to the various portions of the 

 digestive tract. The upper part of the stomach is laminated. The lower and larger 

 part is enclosed by the liver, a not very compact mass, which bears on both the upper 

 and lower side, but only here and there, yellow follicles of the hermaphrodite gland. 

 The large and strong intestine issues from about the middle of the hepatic mass, runs 

 forwards, and then turns to the right. Internally it is strongly laminated. The 

 anterior genital mass is small (3 '5 x 2*5), and the mucous and albumen glands not 

 much developed. The vas deferens is moderately long and not much convoluted ; the 

 verge straight and conical ; the spermatotheca round and not large. 



This form is probably an immature specimen of T. c/iallengeriana Bergh, 

 recorded from the west coast of Patagonia. Differences are not wanting, particularly 

 in the number of the branchiae, which are only 1 1 here, whereas T. challengeriana has 

 25-30, but I do not think there is sufficient ground for creating a new species, and the 

 animal cannot be certainly identified with T. appendiculata, to which it shows resem- 

 blances. The peculiar shape of the head and position of the rhinophore sheaths is 

 perhaps not natural. 



TRITONIELLA. 



MOST of the characters are as in Tritonia, but the dorsal margin is wide and bears not 

 foliaceous tufts, but simple unbranched prominences, which have a few lamellae on the 

 under side. Some of the specimens are exceptionally well preserved, and it seems clear 

 that no appendages have been lost. The back bears a median longitudinal ridge and 

 some irregular accessory ridges and tubercles. On the frontal veil are only slight 

 prominences and indentations. The jaws are not denticulate ; the radula is fairly 

 wide with a median tooth. The stomach bears plate-like ridges, which, however, are 

 not detachable. 



The collection contains two species, which are best distinguished by the dentition. 

 In Tritoniella belli (named in honour of Professor F. Jeffrey Bell, of the British 

 Museum) the rhachidian tooth is broad, with a large cusp and rudimentary denticu- 

 lation, and the first lateral is as in Tritonia. In Tritoniella sinuata the first lateral 

 does not differ much from the others, and the rhachidian tooth is an inconspicuous flat 

 plate. 



