TRITONIIDAE. 



11 



in front. It bears two very distinct, grooved tentacles of the Tritonia type, and 

 a number of faint indentations, apparently representing undeveloped tubercles in 

 different stages of growth. Down the centre of the back runs a crinkled ridge, 

 which is connected with the right but not with the left rhinophore probably an 

 abnormality in this specimen and gives off a short asymmetrical side ridge on the 

 right, about half-way down the back. Between the rhinophore pockets is a large, 

 round tubercle. The back is covered everywhere with smaller tubercles, as are also 

 the sheaths of the rhinophores, which are directed vertically. The genital orifices 

 are about 9 mm., and the anus about 15 mm. from the head. 



The central nervous system is as in T. belli, but the granulations of the ganglia 

 are not very distinct. No eyes are visible. 



The body walls are thick. The jaws are more elongate than in the other species 

 and do not form a circle. They are not regularly denticulate, but the black edges bear 

 numerous asymmetrical prominences. The radula is dark brown in front, yellow 

 behind. The formula is 56 x about 70.1 .70. Contrary to what is usual in Tritonids, 

 the central tooth (Fig. 9) is hard to see, and is hidden by the laterals which bend over 



FIG. Q.Tritoniella 



sinuata RHACHIDIAN 



TOOTH. 



FIG. 10. Tritoniclla sinuata THREE LATERAL TEETH. 



FIG. 11. 



Tritoniella sinuata 

 VERGE. 



it. It is a flat plate with only faint indications of cusps. The laterals (Fig. 10) are 

 thick, rather irregular in outline, and often with a kink in the back. The first lateral 

 shows hardly any difference from the others. 



The salivary glands are about 6mm. long and 2mm. broad. The stomach contains 

 a girdle of 14 flat, broad ridges, plate-like, but soft and not detachable. They are 

 about 4mm. long and 1*5 broad, and bear 7-10 irregular transverse striae. They are 

 not like those of the other species on account of their width and flatness. The stomach 

 is full of black matter and the greater part of it is enclosed in the dark-grey liver, which 

 is itself covered in many, but not all, parts by the reddish-yellow hermaphrodite gland. 

 The intestine is laminated internally. 



The reproductive organs resemble those of the other species, except that the verge 

 (Fig. 1 1 ) has a broad flat top from which rises a conical point. The albumen and 

 mucous glands are not much developed ; the spermatotheca is elongate and tapering ; 

 the vas deferens extremely long and coiled. 



The dentition seems to distinguish this species from T. belli, and there are also 

 differences in the jaws, reproductive organs and stomach plates. Probably also the 

 external appearance, particularly the mantle edge, is different. 



