26 



SPONGIOCHITON. 



moderate, indented by the sculpture of the outside. Girdle very 

 thin, rather expanded, smooth. (Cpr.) 



Length 13}, breadth 7} mill. ; divergence 120. 



Island of Bohol, Philippines' 



Chiton coarctatus SOWERBY, P. Z. S. 1841, p. 62. REEVE, Conch. 

 Icon., t. 20, f. 127. Leptoplax coarctatus CPR. MS., and Lept. 

 rubrotincta CPR. MS. olim. 



This might be regarded as an extremely delicate Katherina, but that 

 the valves are thrown forward and the tail-plate is Ischnochitonoid 

 rather than Mopaloid. It differs from Fannia as Ischuochiton does 

 from Chiton, in the extreme thinness and general smoothness of the 

 sharp teeth and in the non-dentition of the sinus. I have seen no 

 other regular Chiton in which the insertion plates are tinted, the 

 head valve having only four slits, and the tail valve with so long a 

 lamina, unfissured, at the anterior sides. ( Cpr.) 



Carpenter at first described this form under the name rubrotincta 

 but he discovered its identity with C. coarctatus by an examination 

 of the type of the latter. The sculpture varies much ; sometimes 

 there are a few large grains, sometimes many smaller ones. 



Genus VI. SPONGIOCHITON Carpenter. 



Spongio chiton CPR., Table of Regular Chitons, 1873. DALL, 

 Proc. U. S. Nat. Mus. 1882, p. 272, 283, 286, 289, 290. 



Valves partly immersed ; insertion plates acute, Ischnoid ; sinus 

 large, smooth ; mucro median, flat ; girdle spongy, produced forward. 

 (Cpr.} 



S. PRODUCTUS Carpenter, n. sp. 



Shell oval, the valves immersed two-fifths of their width ; exposed 

 portion rubicund, flat, the jugum arcuate, paler. Lateral areas 

 scarcely defined. Entire surface sculptured with prominent pebbles, 

 worn at the jugum. Mucro submedian, flat. 



Interior : posterior valve with 6, central valve 1, anterior valve 

 5 slits; teeth long, acute, scarcely serrate; sinus wide, smooth, 

 extremely deep. Eaves narrow, scarcely grooved. 



Girdle produced in front, spongy, sparsely covered with chaffy 

 scales and translucent hairlets. 



Length 25, breadth 161 mill. ; divergence 130. (Cpr.*) 



New Zealand (Mus. Cum. no. 50). 



