60 ISCHNOCHITON. 



and /. magdalenensis is that the latter has radsioid valves and coarser 

 girdle scales. Carpenter's description is given above, and the fig- 

 ures represent the type specimen. 



The foot is produced forward, and the gill row is short at both 

 ends. 



I. ALATUS Sowerby. PI. 16, figs. 1-5. 



Shell much elongated, narrow, elevated, rather thin. On a light 

 fleshy buff or greenish ground it is delicately marbled and mottled 

 with olive or olive-green. The sculpture consists of longitudinal 

 close, narrow ridges, which are finer on the dorsal ridge, and change 

 to an irregular granulation on the lateral areas and terminal valves. 

 The lateral areas are decidedly raised; the jugal area is divided 

 from the pleura by a change in sculpture, which becomes coarser 

 and more or less divaricating, sometimes forming a cellular pattern 

 at the edges of the jugal area and on the slopes of the lateral areas. 



Interior rose-pink, rarely almost white ; anterior valve having 9, 

 central 1, posterior valve 9 slits. Teeth sharp, eaves moderate, 

 solid. Sutural plates large, rounded ; sinus very deep, narrow. 



Girdle wide, thin, covered with fine, even, short, striated solid 

 scales. 



Length 57, breadth 16 mill. 



Length 40, breadth 16 mill. 



Islands of Siquijor and Zebu, Philippines, under stones at low 

 water. 



Chiton alatus SOWERBY, P. Z. S. 1841, p. 61. RVE, Conch. Icon, 

 t. 8, f. 45. Ischnochiton alatus GRAY, P. Z. S. 1847, p. 127, and 

 /. altus Gray, Guide, p. ] 82. Stenoplax alata CPR. MS. 



The solid, deeply striated scales of the girdle are very character- 

 istic, as is also the sculpture. The pattern of color is an indefinite 

 and variable mottling. Figures 3, 4, 5 are drawn from a typical 

 specimen received from Sowerby. Figures 1, 2 are from draw- 

 ings made for Carpenter, and represent the scales as much more 

 elongated, and the head valve as less ernarginate. I am disposed 

 to believe that this last peculiarity is a mistake. 



The sole is produced forward as far as the mouth; head fleshy; 

 veil copious, neck lappets long. Gills about one valve's breadth 

 removed from neck and the same at tail. Vent inconspicuous. 

 Foot fleshy, projecting. 



