II No. I II TON. 



r_' ', l.ivadtli 74 mill. 

 Leii-th IS. luvadih ID' mill. 

 liritlnh mid Scandinavian iSV./x. m//-// /" /,.///, //. XO///A /o /; 



/\ / 



Chiton etfMTtffll LlN* N'at. xii, /rx/r Hanky. 



Conch. ]>. 17.- -Low i-:, />nl. .Joimi. ii, p. 9 

 II \NI.KY, Hist. r.i'il. Moll, ii, |>. -ID'J, (. .V\ f. 1, (T. ni'iryiifif' 

 plate*. r. Hinryhntln* IV.N \.\ M, P.rit. /ool. iv, p. 71. t. ::;, f. 2, 

 and of MONT., Sown., IJ\ i:. and .1 1:1 i 1:1 IB, Brft ( kmch, iii, p. 2'Jl , 

 t. 56, i'. 5j P. /. S. ISS'J, p. 669. C. marginatus M; 

 Moiuis, Knuna der Kieler Bucht, ii, t. 1, f. 1-5. Craspedoch'ln* 

 ma ryln.it u SARS, Moll. Arct. Norv. ]>. 11"), t. 20, f. 16 ; t. 2, f. L'. 

 Trachydermon mt try hiatus CPR., New Eng. Chitons, p. 1 

 Trachijdermon. cinereus CPR. MS. p. 15. DAM., Proc. I 

 Mus. 1878, p. 323. NOT Lepidopleurus cinereus SARS, /. r., t. 7. t'. 

 8. Chiton, circmnrulliitit.* Hi;i:vi:, Conch. Icon. t. 27, f. K 



This species may be known by the evenly shairreened surtin-r. 

 which is quite different from other North Atlantic Trachydermons. 

 Tr. dentiens Gld., which Jeffreys considers the same as Hnereiift, 

 differs in sculpture, color, and the shorter form. There are a num- 

 ber of old and more or less doubtful synonyms, such as Ch. 

 fiiscatus Brown, 111. Conch. G. B. p. 66, t. 21, f. 17 ; and Jeffreys 

 quotes also cimex Chemn. and cimicinus Landt. 



Carpenter seems to have supposed that the gills of this species 

 did not extend forward beyond the middle of the foot, but I have 

 determined by the examination of alcoholic specimens, one of which 

 is drawn on pi. 7, fig. 57, that they extend nearly to the head, 

 being composed of 16 or 17 plumes on each side. They are also so 

 figured by Meyer & Mobius. In this character, cinereiu di 

 from albus and ruber, in which species the gills are median. 



Carpenter, having examined the type of C. circumra/lnf 

 writes that he is satisfied that it is merely a cinereus. The locality 

 given by Reeve is no doubt wrong. 



Yar. variegatus Phil. PI. 7, figs. 58, 59, 60. 



Smaller, with triangular sutural laniinir. Anterior valve having 

 8 or 9, posterior valve having 7 or 8 slits in the insertion plates. 

 Length 8, breadth 5, alt. 3 mill. 



Mediterraii( ^ 



