328 PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



and fiirnislied at its extreme margin witli a fringe of fine spiny hairs or 

 spicules, as in T. marmorea. 



? Tonicella Sitkensis. 



Chiton Sitkensis Midd. Bull. Acad. Sci. St. P^tersb. vi, p. 121, 1846; Mai. Ross. 



i,p.ll2,t.xiii,f.l-2,1847. 

 Tonicia Sitkensis H. & A. Adams, Gen. Eec. Moll, i, p. 474, 1854. 

 Not Chiton Sitkensis Reeve, Conch. Icon. si>. 55, 1847. 



IT. t. externa depressa; tegmentum leeviusculum, areis lateralibus 

 indistinctis, sub lente si)arsim granulosum, rubicunduni; limbi Isevius- 

 culi epidermis zonalis submicroscopio stroma exhibet si)inulis latenti- 

 bus erectis munitum; v. ant. 8-, v. post. 10-, v. centr. 1-fissata; branchiae 

 posticse, parcne, no. circ. 24. Lon. 10, Lat. G mm. Div. 130°. 



Hah. — Sitka, one specimen (Midd.). 



The above species described by Middendorf, if not a variety of one of 

 the others, has not yet been identified or collected by any other natural- 

 ist. His description difiers very much from his figures, while the ante- 

 rior teeth are figured as grooved outside; if correct, an unusual charac- 

 ter. It is said to be nearest to T. submarnioreus, and may well be a 

 young specimen of one of its numerous varieties. 



Genus SCHIZOPLAX Ball. 



ScUzoplax Dull, Proc. Nat. Mus. p. 2, Jan. 1878. 



Tonicia sp. H'. & A. Adams. 



Schizoplax Cpr. MS. (subgenus of Tonicella). 



Testa et zona Tonicellte simulans; valvae centrales sulco jugali medi- 

 ano, antico argute incisaj ; branchijB feubambientes. 



For this remarkable form, which is distinguished from all other known 

 Chitons by the median slit in all the central valves, I propose to adopt 

 the MS. name suggested by Dr. Carpenter on Middendorf 's figures, rais- 

 ing its value, however, to the rank of a genus. The specimens obtained 

 by us appear to be the first obtained by any one since the original spe- 

 cimens of Middendorf. 



Schizoplax Brandtii. 



Chiton Brandtii Midd. Bull. Acad. Sci. St. P(5tei\sl). vi, p. 117, 1846; Mai. Ross. 



i, p. 128, 1847. 

 Chiton {Hamachiton. Steno^cnins) Brandtii Midd. Sib. Eeise, p. 174, t. xv, f. 



1-6, 18.51. 

 Tonicia Brandtii H. & A. Adams, Geu. Rcc. Moll, i, p. 474, 1854. 

 Schizoplax Brandtii Dall, Proc. Nat. Mus. p. 2, Jan. 1878. 



S. t. ovali, longiori, angustiori, satis elevata; jugo rotundato; oliva- 

 ceo-fusca, coeruleo sen strigata, sen maculata sen nebulosa; soe])e irregu- 

 lariter castanoo ; mucrone centr. irregulariter subplanato ; v. post, om- 

 nino satis regulariter excurvata; ar. jug. uonnisi colore defiuitis, ar. lat. 

 vix defiuitis, tota superficie limiore, sub lente conspicue quinc. granu- 



