288 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



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



40&. riaciphora: sinii lato, plauato; zoder setis baud fasciculatim in- 

 structis. Type Chito7i jietholatm So^veThy. South Australia. 



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

 Type G. ohtecta Cpr. New Zealaud. Mus. Cuming, no. 45. 



43a. Acanthochiton : valvis partim tectis; mucrone Ischnoideo; lam. 

 postica rugosim lobata; ar. lat. depressis. Type ilf. plumeus Cpr. Hab.? 

 Mus. Cuming, no. 108. 



4:31). Acanthochiton : valvis per duas trientes immersis. Type S. par- 

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



49. Animal repens, satis elongatum : valvse expositse parvae, omnino 

 contiguai; valva postica infuudibuliformis; mucro retrojectus, termi- 

 nalis; laminae ut in iia^/imna sed obsoletim fissatce; zona Acantbochi- 

 tonoidea. Type Chiton strigatus Sowerby. West Indies. 



49a. Animal et testa Choneplacis similes sed zoua baud porifera. 



Based on Chitonellus striatus and strigatus Sowerby, Concb. 111., figs. 

 62 and 63, wbicb are represented as without i)ores. In the former the 

 valves are separated (as in l^otoplax) ; in the latter they touch (as in 

 Ghoneplax). 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- 

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

 order in tropical waters, as is Gryptochiton 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 ; ^ = irregular. 



