2 C/ECILIOIDES. 



calloused. Animal blind, or at least without pigmented eyes. 

 Jaw composed of many narrow plaits. Radula with 11, 1, 11 

 teeth in C. acicula, 18, 1, 18 in 0. gundlachi, the central tooth 

 much smaller than the laterals, with a tricuspid reflection. 

 Laterals symmetrical, tricuspid. Marginal teeth low, wide, 

 with two low, denticulate cusps. The genitalia, as figured by 

 Lehmann for C. acicula (pi. 15, fig. 1) have the duct of the 

 spermatheca very short. An appendix, enlarged at the end, is 

 terminal on the penis. There is also a short accessory organ 

 anteriorly on the penis. 



Type C. acicula Mull. Distribution, Europe and most tropi- 

 cal and subtropical countries. 



An excellent account of Cascilioides acicula has been given by 

 Mr. L. E. Adams, as follows: " Methods of Progression. Usually 

 the shell is dragged along the ground after the animal, though 

 more rarely it is lifted to a horizontal position (pi. 1, fig. 6). 

 On two occasions I observed the animal protrude its head under 

 the shell towards the spire and progress in that direction, forc- 

 ing the shell along the ground in front of it, apex first, and then 

 lift the shell over its head at an angle of about 45 degrees, and 

 continue its march in that position (fig. 5). The progression 

 is always by slow jerks, and not a continuous glide. I have 

 not observed the shell carried in the position of Jeffrey's figure 

 (British Conchology, Vol. I, pi. 7, fig. 18), though Nilsson 

 says * the animal sometimes carries its shell erect, but generally 

 drags it along depressed.' 



" Texture and Form of the Animal. I was much struck with 

 the extremely flexible and elastic nature of the animal. I have 

 observed one emerge from the shell as it lay flat, on a hori- 

 zontal surface, and make a complete circle with its head and 

 tail, without moving the shell. It is also remarkable how far 

 the animal will protrude from the shell, and how slender an 

 attachment connects the head and foot with the part within the 

 shell. The end of the tail is often curled up. Along the neck 

 ;ind down the front of the head are two mucus sulcations on 

 either side of the dorsal line (pi. 1, fig. 8). The tail is pointed 

 and sharply carinated; from the dorsal ridge mucus sulcations 

 descend to the lower edge (fig. 7). 



