316 



MOLLUSCA 



The anus is medial, and right and left of it are the openings of the neph- 

 ridia and sexual organs. The sexes are separate, the gonads unpaired, 

 while, corresponding to the paired arrangement of the gills, there are two 

 auricles to the heart. Trachydermon,* Amicula* Cryptochiton* 



B 



FIG. 315. Lhiton squamosus, dorsal view (after Haller). A, the entire animal 

 B, after removal of shell and viscera; a, anus; C, brain; K, ctenidia; o, mouth; P, pedal 

 nerve cord; pi. pleurovisceral nerve cord. 



a. .... 



FIG. 316. FIG. 317. 



FIG. 316. Eye and aesthetes of Acanthopleura spiniger (after Moseley). 0, 

 macrassthete; b, micraesthete;/, calcareous cornea; g, \ens;h, iris; k, pigmented capsule; 

 n, p, nerves; r, retina. 



FIG. 317. Neomenia carinata, ventral and side views (after Tulberg). a, anterior; 

 b, posterior; c, ventral groove. 



Sub Class II. Solenogastres (Aplacophora). 



Wormlike forms without a shell (occurs in the larva of Dondersia) ; instead of 

 a foot there is a longitudinal ventral ciliated groove; the radula may be lost; in 

 Conchoderma it bears but a single tooth. The gills are either small or wanting. 

 The usually hermaphrodite animals have the gonads emptying into the peri- 

 cardium and thence by the paired nephridia ( ?). Marine, living in ooze or sand. 

 Chatodcrma,* Neomenia, Dondersia. 



