3338 



THE MOLLUSKS OR SHELLFISH 



i 



y 



Gleba cordata 



acute point. This narrowed portion is generally wanting in adult shells. In the 



soft parts it closely resembles Clio, and it is chiefly on conchological grounds that 



it is separated. The genus 

 Cavolinia is perhaps the com- 

 monest of all. The shell is 

 generally pale horny brown, 

 often globose, composed of a 

 ventral and dorsal plate, 

 which are united inferiorly, 

 but not along the sides or 

 above. The dorsal piece is 

 fiattish, and the ventral gen- 

 erally very globose. The 

 shell is produced into a spine 

 behind, and the sides gener- 

 ally terminate posteriorly in 

 sharp points or spines. The 



a. Body; b. Fin; e. Proboscis. animal somewhat resembles 



Clio in its external character- 

 istics, but is remarkable for the presence of lateral prolongations of the mantle, 



which project through the lateral slits in the 



shell. Eight species are recognized by Dr. 



Pelseneer. C. tridentata, C. uncinata, C. 



globosa, and C. trispinosa are the best 



known. 



In the family Cymbuliidce the shell is very 



different from that of other Thedosomata. It 



is cartilaginous or gelatinous, bilaterally sym- 

 metrical, and somewhat resembles a slipper 



in general form. It is very easily detachable 



from the animal, and consequently a number 



of species, which in reality belong to this 



family, have been characterized as shell-less. 



Pointed at the ventral extremity and truncated 



at the dorsal end, it is covered with acute 



spine-like tubercles arranged in longitudinal 



series. The modified foot, or fins, are large 



and rounded. The animal is furnished with 



a radula. Of Cymbulia, two species are 



known. C. peroni is common in the Mediter- 

 ranean, and it probably also occurs in the 



Atlantic. The second species, of which only 



the shell is known, was found in New Zealand. 



r~ J, T j* ~A /"J J, 4.1. -a. Mouth; b. Sexual organ; c. Reflexed mantle; 



Lymouliopsis and Lrleoa are the two remain- 

 ing genera of this family. 



ANIMAI, OF MAI,E PERIWINKI.B, WITH 

 THE SHEU, REMOVED. 



d. Vent ; e. Kidney ; f. Slime gland ; g. Gill ; 

 h. Heart ; m. Shell muscle ; p. Foot. 



