404 



APLACOPHORA 



CHAP. 



H. Cryptoidea. — With double sutural laminae ; Crypto- 

 co7ichus, Amicula, Qryptochiton. 



am 



t 



7n... 



r »^ 



.,7n 



Fig. 265. — Chitonellus fasciatus Quoy ; ant, anterior end. 



I. Chito7ielloiclea. — Posterior valve funnel shaped ; laminae 



thrown forward ; Chitonellus^ Choyieplax. 

 Sub-order 2. Aplacophora. — Animal vermiform, foot 

 absent, or a mere groove, cuticle more or less 

 covered with spicules. 



According to Marion, one of the principal 

 authorities on the group, the Aplacophora 

 are perhaps Amphineura whose development 

 has been arrested at an early stag^e, their 



Fig. 266. — iV^eo?nema . , . *^ ° 



caHnataTxAih.: a, v'orm-like exterior being 



anus; gr, ventral ^^^q ^q adaptation tO SUr- 

 groove; 7n, mouth. n^i ^ 



roundings. ihey have 

 hitherto been found chiefly in the N. Atlantic 

 and Mediterranean, generally at considerable 

 depths, and often associated with certain 

 polyps in a way which suggests a kind of 

 commensalism. 



Fam. 1. Neomeniidae. — Foot a narrow 

 groove, intestinal tube without differentiated 

 liver, kidneys with common exterior orifice, 

 sexes united, ctenidia present or absent. 

 Genera : Neomenia (Fig. 266), Paramenia^ 

 Proneomenia^ Ismenia, Lepidoinenia, Don- 

 dersia. 



Fam. 2. Ohaetodey^matidae. — Body cylindrical, no ventral 

 groove, liver a single sac, kidneys with separate orifices into the 

 branchial cloaca, two bipectinate ctenidia. Single genus, 

 Qhaetoderma (Fig. 267). 



Fig. 267 .—Chaetoderma 

 nitidulum Lov. : a, 

 anus ; m, mouth. 

 X 3. 



Order II. Prosobranchiata 



Visceral loop twisted into a figure of 8 (streptoneurous), right 



