PLACIPHORELLA-PLAXIPHORA. 311 



Illustr., f. 6. REEVE, Conch. Icon., t. 3, f. 13. Mopalia blain- 

 mllii GRAY, P. Z. S. 1847, p. 69. Mopalia blainvillei CARPENTER, 

 MS. and in DALL, Proc. U. S. Nat. Mus. 1878, p. 303. Placiphor- 

 ella blainvillii DALL, 1. c. 1886, p. 210, 211. 



This large species is nearly allied to P. velata of California, but it 

 differs in having the lateral areas simply somewhat swollen, and not 

 excavated in the middle. The sinus between the sutural plates is a 

 shallow wave, but it deepens on the two or three backward valves, 

 as in the Californian species. The description given above is com- 

 piled from Carpenter's notes on the type specimens. 



P. PETASUS Reeve. PI. 66, fig. 25 (enlarged.) 



Shell small, somewhat abbreviately ovate. Valves with a polished, 

 slightly beaked triangular area in the center, roughly granulated on 

 each side. Bright scarlet. Ligament very broad, especially in front, 

 also bright scarlet, beset here and there with short hairs and bristles. 



Length 1, breadth f inch. (Eve.) 



Cape Rivers, Celebes (Belcher.) 



Chiton petasus REEVE, P. Z. S. 1847, p. 25 ; Conch. Icon., t. 26, 

 no. 114, fig. 112, (not 112 on plate of details, nor 114) ; July, 1847. 

 ADAMS & REEVE, Zool. of the Voy. H. M. S. ' Samarang,' Moll., 

 1. 15, f. 11. 



Referred to this genus on account of the peculiar girdle. A single 

 specimen was collected. The characters of the interior have not 

 been made known. 



Genus XXXI. PLAXIPHORA Gray, 1847. 



Plaxiphora GRAY, P. Z. S. 1847, pp. 65, 68, 169. SHUTTLEW., 

 Bern. Mittheil. 1853, p. 69. H. & A. ADAMS, Gen. Rec. Moll, i, 

 p. 481. Placiphora CPR., MS. and in DALL, Proc. U. S. Nat. Mus. 

 1881, p. 284. Placophora DALL, Cat. Mar. Moll. S.-E. U. S., p. 174 ; 

 not Placophorus Mulsant, 1873 (Trochilidce). Euplaxiphora SHUT- 

 TLEW., 1. c., (proposed for biramosus and petholatus). Euplacipliora 

 CPR., 1. c., (type P. petholata'). Chcetopleura (part) ROCHEBRUNE, 

 Miss. Sci. du Cap Horn, 1882-1883, vi, Zool., Polyplacophores, p. 

 135 (1889), not Chcetopleura Shuttlew. ! 



Valves mostly exposed, all having insertion-plates developed, that 

 of the anterior valve normally with 8 (sometimes 7-9) slits (except 

 in the subgenus Placophoropsis which has many slits). Median 

 valves 1 slit. Posterior valve having the insertion-plate smooth, 



