NUTTALLINA. 277 



posterior valve 13 slits ; teeth blunt, finely and deeply pectinated out- 

 side and at the edge. Eaves solid. 



Girdle broad, compactly covered with shining, deeply sulcated 

 scales, measuring about one-third of a millim. in breadth, and the 

 terminal margin of each is smooth (fig. 13.) 



Length about 16, breadth 10 mill. ; divergence about 105. 



Eed Sea. 



This species has far fewer ribs on the terminal valves than C. 

 adenensis Smith, although the lateral areas have more ribs. The 

 girdle scales are coarser than in other species, and they have the 

 peculiarity noted in C. shuttleivorthianus, of being smooth at the 

 distal end. I have seen no Chitons of other genera having this 

 feature. The second valve has several slightly diverging riblets at 

 the front of the dorsal area. The teeth are as deeply pectinated as 

 in any species of typical Chiton or Acanthopleura ; and it is by no 

 means impossible that the species belongs to the former genus. I 

 have preferred to retain it in Callistochiton on account of the peculiar 

 sculpture, and the relation in which the slits stand to the ribs. 



The type is in the collection of the Academy. 



Var. SAVIGNYI Pilsbry. PL 60, fig. 16. 



This form is known to me by Savigny's figures, which indicate a 

 species closely resembling the last. The head valve has 11, the 

 lateral areas two ribs ; the tail valve is smaller, having 9 ribs ; 

 central areas with about 9 ribs on each side, and a rather wide 

 smooth tract in the middle. Scales of the girdle sulcate, with 

 .smooth outer edges. 



SAVIGNY, Descript. de 1'Aegypte, Gasterop., t. 3, f. 8-1, 8-2, 8'3. 



Genus XXIV. NUTTALLINA Carpenter, 1879. 



=Nuttallina plus Middendorfia plus Beanella Cpr. 



Valves exposed, granulated, the - lateral areas having 2, head 

 valve numerous low radiating ribs ; insertion-plates sharp, the slits 

 corresponding in position to external ribs. Mucro behind the 

 middle, the posterior teeth directed forward. Eaves and sinus very 

 spongy. Girdle varying from spiny to scaly. 



This well-defined genus probably has the same apparently 

 anomalous distribution as the coral-red Leptothyras ; species being 

 found in the Mediterranean, the Japanese Seas, and the coast of Cali- 



