PIIYLLIDIANA. MOLLUSCA. CHITON. 151 



SO as to resemble the finest shagreen. Valves moderately cari- 

 nated, and with a minute beak ; distinctly marked with lines of 

 growth, and a feeble diagonal ridge often divides each side into 

 two triangles ; anterior valve crescentic, with about twelve 

 marginal teeth. Margin membranous, yellowish, covered with 

 beaded granules. Length -^-^ inch, breadth ^-^ inch. 



Found in the stomachs of fishes in considerable numbers. 



This shell was first discovered on this side the Atlantic by Mr. Joseph 

 P. Couthouy, and supposed by him to be new. But it agrees in all 

 respects with Mr. Lowe's figure and description of C. aselloides ; and 

 Mr. Sowerby, on an examination of our shell, accords with me in 

 opinion that it is that shell. Mr. Lowe subsequently states (Zool. 

 JoLirn., iii. 79.) that his species " is clearly identified with C. albus of 

 Montagu." But, as it is only while when divested of its pigment, the 

 name aselloides is much more descriptive. 



The ridges, edges, and interstices of the valves usually have the pig- 

 ment worn off", so as to present a yellowish-color. The beaded margin 

 distinguishes it from all our other species ; but it is rare to find the 

 margin unimpaired. 



Chiton Emersonia'nus. 



Shell ovate-ohlong, white ; valves reniform., each with a central 

 cordiform.) sculptured area, the remainder covered with a dirty mem- 

 brane, with two rows of hairy tufts at the margin ; anterior valve 

 emarginate. 



Figure 19. 



State Coll., No. 132. Soc. Cab., No. 2351. 



Chiton Eniersonii, Couthodv ; Bnst. Journ. JVat. Hist., ii. 83, pi. 3, f. 10. 



Shell ovate-oblong, broadest behind ; of a light drab-color ; 

 valves eight, kidney-shaped, the extremities being rounded and 

 the posterior margin deeply arched ; posterior valve narrowed and 

 excavated at the tip ; on the centre of each valve is a small, heart- 

 shaped area, beautifully sculptured with bead-like granules, three 

 or four series of which are parallel to its border, and the central 

 ones on each side are arranged in a somewhat concentric manner ; 

 the beak is elevated and pointed, and smooth or slightly striated ; 



