PROCEEDINGS Oh' UNITED STATES NATIONAL MUSEUM. 333 



each side. Xo veil, (rillrow.s tliieequarters ii.s long as the foot, each 

 containing about forty branchia'. 



(In Lepidoradsia ausfraUs, the gill-rows were found to extend the 

 whole length of the foot, and to contain forty-seven branchiae in each. 

 Mantle-edge plain, thin; muzzle plain, semicircular, without a veil; 

 the ovarian openings situated close on either margin of the anus.) 



ACANTHOIDEA. 

 Genus NUTTALLINA Cpr. MS. 



Lorica elongata, valvis autice projectis; mucro posticus, elevatus; 

 laminae acutae, kcves, (nisi v. post.) elongatai; v. centrales bifissatae; 

 sinus haud laminatus, planatus 5 zona spinosa. 



From Acanthopleura this genus difiers in the smoothoess of the sharp 

 teeth, in their great length and Eadsioid slitting; in the thrown-back 

 mucro, which often projects beyond the margin ; in the throwing forward 

 of the rest of the shell, as in Katherina, and in the deep spongy tlat 

 sinus which interrupts the sutural laminae. The name is given in honor 

 of the late Thomas Nuttall, Esq., once professor of natural history at 

 Harvard College, and the original discoverer of the typical species, as 

 well as many others of the shells and plants of California. (Cpr.) 



Nuttallina scabra. 



Chiton scaber Reeve, Conch. Icon. Mon. CMton, pi. xvii, f. 106, 1847. 

 Chiton calif omicus (Nutt. MS.) according to Carpenter. 

 Not Chiton calif omicus (Nutt. MS.) according to Reeve. 

 Acantlwplcura scabra Cpr. Suppl. Rep. Br. Assoc. 1863, p. 649. 



N. t. mucrone postico, sed haud terminali, maxime trans marginem 

 posticum elevate; v. post. 7-8-, v. ant. 10-11-, centr. 2-flssatis; dent. 

 a«utis, laevibus, (nisi postice) praelongis, antice valde projectis; valvis 

 centralibus dent. post, minoribus; subgrundis parvis, haud sulcatis; 

 sinu altissimo, lato, planato, spongioso, haud laminato; zona lata crassa; 

 spinis testaceis curtioribus densissime obsita. Lon. 36, Lat. 10 mm. 



Hah. — Vancouver district, south to California, probably in the south- 

 ern islands of Alaska; at and above high-water mark, in crevices of the 

 rocks; at Monterey abundant. 



This singular species, not yet obtained from Alaska, but which will 

 probably be found there, like some Litorinas, seems habitually to prefer 

 positions where it can at most be reached by the spray in storms, on ex- 

 posed headlands, where the breeze comes in damp and cool from the sea. 

 The pointed valves overlap each other so much that when the creature is 

 curled up they project from the girdle, giving a pectinated outline, un- 

 usual in Chitons. The valves are almost always eroded, even the prom- 

 inent mucro is often hollowed out, and the sculpture can rarely be seen 

 except in young specimens. The color is grayish or brownish, with 

 whitish streaks ; the girdle has the aspect of dead brownish-black moss, 

 sometimes with ashy spots at the sutures. 



