CH.ETOPLEURA. 29 



suture. The valves are minutely sculptured with very minute 

 granules in lines which diverge slightly at the jugum, more upon 

 the sides of the central areas, divaricate on the border between 

 central and lateral areas, and are radiating upon, the lateral areas 

 and terminal valves. The umbo of the tail valve is low, somewhat 

 anterior. 



Interior white with a brown stain at the back edge of each valve. 

 Anterior valve having long insertion plates which are distinctly 

 crenulated outside, and have 9-10 slits, central valves with 1 slit, 

 post, valve with 7-9 slits. Sutural plates very broad, connected 

 across the sinus by a narrow plate ; eaves narrow, short, not spongy. 



Length 38, breadth 26 mill. 



Lima, Peru; Chili; to Cape Horn. 



Chiton peruvianus LMK., An. s. Vert, vi, p. 321 ; ed. Dh., vii, p. 

 491. Barnes, Amer. Jour. Sci. vii, p. 10, t. 3, f. 2. SOWB., Conch. 

 Illustr. f. 44. REEVE Conch. Icon. f. 50. Chaetopleura peruviana 

 Lm., SHUTTLW., Diagn. n. Moll. nr. 4, p. 67. ROCHEBR., Moll. 

 Cap Horn, p. 135. Acanthopleura peruviana Lm., TAP. CAN., 

 Viag. Magenta, p. 77. 



This form is readily known by its girdle covering and sutural 

 fringes of long black hairs. The sutural plates are strongly devel- 

 oped, slightly recalling Leptoplax. The hair is crisp and coarse, 

 like that of a horse's tail. The gills extend forward to the head. 



C. HENNAHI Gray. PL 12, figs. 47, 48, 49 ; pi. 17, fig. 39. 



Shell oval, rather depressed, dorsal ridge obtuse, side slopes 

 nearly straight. Color variable, but generally either reddish-brown 

 marked with red, or greenish-white marked with brown ; surface 

 smooth to the naked eye. Girdle leathery, covered with short hairs, 

 which may readily be rubbed off. 



The median valves are about four times as wide as long; the 

 lateral areas are only weakly indicated ; the tail valve is depressed, 

 with the slightly prominent umbo in front of the middle, the pos- 

 terior slope concave. The sculpture consists of closely beaded fine 

 separated threads, which are longitudinal on the central, radiating 

 on the lateral areas and end valves; under this may be seen an 

 excessively fine, close shagreening of the whole surface. 



Inside white, each valve marked with brown under the beaks. 

 Sutural plates of equal width from the outer angle of the valve to the 

 rather shallow sinus. Ant. valve having 13, central valves 1, post. 



