Acanthopleura. | AMPHINEURA. 45 



are calcareous, and either black or white ; the black spines are fre- 

 quently longer and straight, the white spines short, mingled with a 

 few much larger ones, shaped like the shell of Cadulus. Colour dull, 

 ashy, or brown, generally with a patch of brown on the ridge of each 

 valve, with a pair of whitish, buff, or pinkish stripes. Interior sea- 

 green or lead-blue, fading to nearly white on the sutural plates ; each 

 median valve with a purple-black tract between the sinus and the 

 summit of the callus, square or 2-branched at the ends, anterior valve 

 having normally 8-10, central 1 (rarely 2), posterior valve 9 (occa- 

 sionally 7-14) slits ; teeth long and very deeply pectinated outside ; 

 teeth of tail valve short and obtuse, directed forward, very deeply 

 pectinated outside and on the edge ; sinus slightly concave, or convex 

 and notched at the sides, not denticulate. 



Length, 80 mm. ; breadth, 46 mm. Divergence, about 125. 



Type (?). 



Hob. New Zealand. Pitt Island, Chathams. 



Remark. This is the common Chiton of the West Indies. 



Subfam. 3. LIOLOPHURIN.E 



Median and anterior valves provided with eyes, and having well- 

 developed insertion plates with slits, the teeth pectinated outside, 

 not thickened at the edges of the slits. Posterior valve with the 

 mucro posterior and terminal ; its insertion plate obsolete, reduced 

 to a low ridge or flat ledge of callus, which is unslit (except in Schizo- 

 chiton) and continuous posteriorly or interrupted in the middle by 

 a caudal sinus. Gills as long as the foot. 



This group is closely allied to Chitonidce, and has doubtless been 

 derived from the Tonicioid branch of that stock. It is separated from 

 them on account of the degeneration of the posterior valve, and especi- 

 ally of its insertion plate. (Pilsbry.) 



Genus 5. LORICA, H. and A. Adams, 1852. 

 Lorica, H. and A. Adams, A.M.N.H. (2), ix, 355. Type : L. volvox, Reeve. 



Valves exposed, not beaked, the lateral areas and end valves with 

 many fine riblets or pustules. Eyes confined to a single series along 

 the summit of each diagonal rib. Insertion plates blunt, obsoletely 

 pectinated, the slits in head valve not corresponding to external ribs ; 

 sinus very small. Posterior valve having the mucro posterior and ter- 

 minal, insertion plate unslit, obsolete, being reduced to a convex ridge 

 of callus ; posteriorly cleft to the mucro by a deep rounded sinus, 

 or waved. Girdle slit or waved behind, densely scaly. 



This is one of the few genera of " irregular " Chitons having a 

 scaly girdle. The eyes seem to be nearly obsolete, and possibly are 

 not functional, although they still are pigmented. In most speci- 



