282 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



* Type. 



Chiton corrugatus Sandberger fr., Verst. Rliein. Scbicht. Nassau, p. 238, pi. 26, fig. 

 22 a, 1856, not ligs. 22, 22 h, 22 c, 22 d = lisli scales and valves of barnacles, as 

 per typical sixjcimeiis iu Mus. Comp. Zoology, etc. Devonian of Vilmar. 



Cymatochiton Dall. 



Valvis centralibus traiisversis, antice projectis, satis elevatis, jugo 

 acutiore, lateribus planatis; apopbysibus modicis, satis extantibus, valde 

 distaiitibus; sinu jugali latissimo, iucurreiite; uinbonibus extantibus, 

 margiue antico ad jugum valde postice siiiuato. Type C. Lo/tusianus 

 King. 



Tliis represents a LeptocMton witli the valv^es thrown forward. It 

 differs trom Proholccum in the valves being transverse instead of squared, 

 and in the terminal valves being regular instead of waved. The name 

 Cymatodus used in manuscript for this group by Dr. Cari)enter iij preoc- 

 cupied by Newberry (1870). 



Species. 



CymatochUon Loftusianus King, Annals & Mag. Nat. History, I, vol. 14, p. 382 ; Kirkby, 



Proc. Geol. SoclbT^O, p. 607, 611, 615, pi. 16, figs. 31-41. Permian, Tunstall 



Hill, England. 

 Cymatochiton RyckhoUianus Koninck Mss. Types Mus. Comp. Zool. Carboniferous of 



Vis6, Belgium. 

 ? Cymatorhiton tornaticola* Ryckholt, 1. c., p. 45, pi. 1, figs. 1,2,3, 1845. Carboniferous 



of Tournay. 

 f Cymatochiton Scaldeanus * Ryckholt, 1. c, p. 46, pi. 1, figs. 4, 5, 6, 1845. Same locality. 

 f Cymatochiton Howstanus Kirkby, Quart. Jouru. Geol. Soc. 1857, p. 216, pi. 7, figs. 9-13. 



Permian, Tunstall Hill, England. 



This last species is the first undoubted Chiton to put on features com- 

 mon to all the recent forms of the family. 



Until the fall record of his investigations is published, the amount of 

 confusion as to types, discrepancies between figures and specimens, and 

 errors of one kind and another discovered by Dr. Carpenter in his exam- 

 ination of the original types of many of the species can hardly be im- 

 agined. The synonymy is also necessarily left until the complete paper 

 shall be printed. Meanwhile the student is warned that the citations 

 herein actually made are the only ones which are guaranteed to relate 

 to the species named, though there may be, and in most cases are, others 

 ■which might be cited. The preceding (with synonyms) number all the 

 Palaeozoic chitons actually determined to be such up to 1873. 



In the course of the iuvestigation the following species have been 

 found not to be chitons or chitonoid. They belong variously to fish 

 scales, barnacle {Turrilepas) valves, ostracod Crustacea, and some to un- 

 determined organisms. 



* Doubt attaches to iij^e molluscan nature of these two miiiute species, which have 

 Bome crustacean features. 



