NACELLA. 117 



This section differs from Nacella s. s. in having the branchial pro- 

 cesses equally developed all around, and the shell more solid and 

 more intensely colored. 



The dentition is in all essentials similar to that of Nacella s. str. 

 Indeed there are no characters upon which a separation more than 

 specific can be based. At the same time, there is some considerable 

 variation observed among the various species of Patinella, part of 

 which may be specific, part merely individual variation. A large 

 number of radulse must be examined before safe specific characters 

 can be based upon this organ, as it varies just as do the shells. PL 

 74, fig. 5, represents the dentition of N. venosa ; pi. 74, fig. 7, 8, that 

 of X. juegiensis. 



The Xew Zealand species referred by Hutton to Patinella belong 

 to Helcioniscus (q. v.). They have the branchial cordon incomplete 

 in front, and no epipodial ridge has been observed in them, this 

 last character being the main diagnostic mark of Nacella-}- Patinella. 



X. .ENEA Martyn. PL 15, figs. 5, 6 ; pi. 45, figs. 22, 23. 



Shell solid, elevated, ovate, the breadth three-fourths of the length ; 

 apex somewhat anterior, but behind the anterior third, and always 

 somewhat curving forward. Sculptured by 34-38 rather strong 

 radiating ribs, which are typically closely scale-grained, but as 

 frequently almost smooth. Color brownish-ashen with several con- 

 centric dark brown zones ; when worn, of a ferruginous-brown all 

 over. 



Interior lustrous, whitish or of a bronze tint, the center with an 

 irregular red-bronze area, which is generally (but not always) rather 

 small and indistinct. Margin scalloped. 



Length 63, breadth 48, alt. 26 mill. 



Straits of Magellan. 



P. cenea MARTYN, Universal Conchologist i, t. 17. REEVE, 

 Conch. Icon., f. 9. SMITH, Philos. Trans, vol. 168, p. 179, 1879. 

 ? P. rustica PERRY, Conchology, t. 43, f. 2. P. guadichaudi BLAINY, 

 Diet, Sci. Nat. xxxviii, p. 93 (1825.) 



Typical cenea is thicker than var. deaurata ; the dark stripes of the 

 exterior are faint or imperceptible within ; the apex is more central. 

 It is more ovate than var. magellanica, the apex less erect. 



Th,3 description and figures given above, as well as the synonymy, 

 apply to typical cenea only. 



