288 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



40a. =Streptochifon Cpr. MS. Type F. Collei H. Adams. Australia. 



406. Placiphora : sinu lato, planato ; zont© setis baud fasciculatim in- 

 stnictis. Type Chiton petholatus Sowerby. South Australia. 



40c. Placiphora: valvis partim immersis; zona postice emarginata. 

 Type G. obtecta Cpr. New Zealand. Mus. Cuming, no. 45. 



43rt. Aeanthochiton : valvis partim tectis; mncrone Isclmoideo; lam. 

 postica rugosim lobata; ar. lat. depressis. Type M. plmneus Cpr. Hab.? 

 Mus. Cuming, no. 108. 



43Z>. Aeanthochiton : valvis per duas trientes immersis. Type S. por- 

 recta Cpr. Japan. Mus. Cuming, no. 97. 



49. Animal repens, satis elongatum : valvte expositse parvse, omuino 

 coutigufe; valva postica infundibuliformis; mucro retrojectus, termi- 

 nalis; lamiuiie ut in Katherina sed obsoletim fissatre; zona Acanthochi- 

 tonoidea. Type Chiton strigatus Sowerby. West Indies. 



49«. Animal et testa Choneplacis similes sed zona hand porifera. 



Based on Chitonellns striatus and strigatus Sowerby, Conch. 111., figs. 

 62 and 63, which are represented as without pores. In the former the 

 valves are separated (as in Notoplax) ; in the latter they touch (as in 

 Choneplax). The species need examination to confirm the accuracy of 

 the figures, but it is probable that there are both pore-bearing and non- 

 poriferous species among the vermiform as well as the compact Chito- 

 uelles. These last groups are the highest and most active in the whole 

 order in tropical waters, as is Cryptochiton in the north. 



Table I. 

 The following table will exhibit the minor characteristics of most of 

 the recent Chitons in regard to the plan of the insertion plates, number 

 of slits, if any, in anterior, middle and posterior valves; character of the 

 tooth-like projections between the slits; and of the margin of the outer 

 layer overhanging the insertion plates, termed eaves by Dr. Carpenter; 

 all according to the numbers and letters of the preceding list : 



X = many ; -=- = few ; + = or more : >(c = irregular. 



11 



lift 



12 



12a 



13 



14 



15 



16 



Plan of insertion plates. 



(Leptoidea.) 



None 



...do 



Only in anterior valve 



Present in anterior and pos- 

 terior valves. 

 Present in all valves 



Slits in valves. 



{Ischnoidea.) 

 I Regular, branching . 



do 



Minutely divided- . . 



do". 



Kegular, branching . 



do 



Regular, projecting . 

 Regular, branching . 



Teeth. 



None 



None 



Rugose lamina - 

 Smooth lamina . 



.do 



Sharp, normal . 



Eaves. 



None .. 

 None . . 

 Minute 

 ...do.. 



Gills. 



None 



...do 



Propped outside . 



Sharp, normal 



do 



Sharp, long, thin . . 

 Sharp, normal 



Projecting, spon- 

 gy- 



. ..,do 



Broad, spongy... 



do 



Short 



...do 



Minute 



Short. 

 Post. 

 (?) 

 Short. 



Short. 



Med. 



Med. 



(?) 



(?) 



Med. 



Subamb. 



(?) 



Moderate ' Amb 



