I9I3-] 



Ekendranath Ghosh : Mollusca, I. 



211 



length. There are also minute dots of the same colour in the 

 interspaces. The lower third of the mantle presents small elon- 

 gated dots with a very faint trace of a network similar to that in 

 the upper two-thirds. The striping is not symmetrical on both 

 sides. The ommatophores and the tentacles are slaty-blue in 

 colour. The precephalic flap is pale slaty-blue in colour. The foot 

 is pale yellow. 



M easily e)nents. — The measurements of the two specimens in 

 cm. are as follows : — 



I. 

 2. 



3- 

 4- 



9 



10 



II 



12. 



Length along the middorsal line 

 Length along the midventral line after 



straightening the animal 

 Greatest height (ventral) . . 

 Greatest breadth at the same part of 



the body 

 Height of the keel at the junction of 



the posterior one-fourth and anterior 



three-fourths of the length 

 Height of the keel at the junction of the 



anterior one-fourth and posterior 



three- fourths 

 Length of ommatophores 

 Breadth of 



Length of lower tentacle 

 Breadth of lower tentacle 

 Distance of the male aperture from the 



anterior end of the foot 

 Distance between the male and female 



genital apertures 

 Depth of the groove round the foot 



(to tlie margin of the mantle) 



7'i 



5'5 

 •9 



■7 

 •125 



■05 

 ■25 

 •15 

 ■15 

 •I 



'2 



TO 



•2 



5 3 



4-5 



•8 

 •65 



Anatomy. 

 /. Body-wall. 



The body has the shape of an isosceles triangle in transverse 

 section in the middle of its length. The triangle has a short base 

 and the sides slightly concave in their upper one-fourth and 

 markedly convex in their lower three-fourths Towards the 

 posterior end, the sides become more convex than they are in the 

 middle, the body assuming a broadly ovate shape in transverse 

 section. 



The body- wall is traversed by the following blood-sinuses, 

 which pass longitudinally throughout the whole length of the 

 body : — 



(i) A sinus lying in the middle line beneath the keel, and in 

 the middle of the thickness of the body-wall. 



