APPEXDIX-ACM/KIIXT-:. 167 



ACM.KA OXYCHIXA Gould. PI. 73, figs. 96, 97, 98. 



The original figures of this species are not very satisfactory, 

 although Gould's description is very good. Figures are here given 

 drawn from specimens lately collected at Bahia, Brazil. 



The diagnostic characters are, besides the orbicular and rather 

 depressed form, the sculpture, which consists of a variable number 

 of low, rounded radiating ribs (often nearly obsolete), the'enfrVe 

 surface being finely radially striated. The erosion of the surface is 

 generally, so far as my specimens show, extensive, the sculpture 

 being lost to a corresponding degree. The interior is characterized 

 by a black-brown spatula which often has a "tail-piece" similar to 

 the usual head-segment, and nearly always there are broad rays 

 extending to the front and posterior margins from the central spatula. 

 The marginal border is either black or tessellated. This species 

 has a wide distribution along the east coast of South America, ex- 

 tending as far south as Santa Caterina, in S. Lat. 32 30', where it 

 has been collected by Dr. H. von Ihering (see Dall, in The Xautilus, 

 Aug., 1891, p. 44). See also the locality of the synonymous P. 

 mulleri Dkr., this volume, page 43. The name Acimca subrugosa 

 was published by Orbigny prior to the Gouldian name onychina, 

 but the diagnosis given is scarcely sufficient for recognition. It is 

 as follows : 



A. testa ovato-convexiiiscula, striato-cqstata ; striis incequalibus ; 

 albido-virescente zonis fuscis radiata; intus fusco ; margine sub- 

 crenato, lutescente, fusco-maculato. Diam. 18 mill., alt. 8 mill. 

 (Orb.) 



Mr. E. A. Smith has recently described a form closely allied to 

 this species, from the island Fernando Xoronho. It should prob- 

 ably be considered a variety of the A. onychina. 



Var. NOROXHEXSIS E. A. Smith. PI. 73, figs. 93, 94. 



Shell ovate, wider behind, moderately elevated, blackish, painted 

 with pale rays, eroded and black at the apex, which is situated a 

 little in front of the middle ; radiately delicately striated, sculptured 

 with lines of increment. 



Interior blackish within the muscle-scar, toward the apex having 

 a thin whitish callus ; outside of the muscle-scar, nearly to the edge, 

 it is bluish-white ; at the margin narrowly edged with black ; hav- 



