108 AXEL A. OLSSON 



Glycytneris (Tuceta) tessellata (Sowerby), Hertlein and Strong, 1943, Zoologica, vol. 



28, pt. 3, pp. 151, 152. 

 Pectunculus minor d'Orbigny, 1846, Voy. Amer. Merid., vol. 5, pt. 3, Mollusqucs, p. 62S, 



No. 709. (Not P. minor I. Lea 1833) 

 Glycymeris chemnitzii Dall, 1909, Proc. U. S. Nat. Museum, vol. 37, No. 1704, p. 253. 



New name for P. minor d'Orbigny. 



Shell orbicular, triangular, rounded or expanded ventrally, narrowed 

 inward dorsally, the submargins somewhat appressed, straight, the anterior 

 margin rounded, the posterior more produced and angled at the end, especi- 

 ally if viewed from within. Surface sculptured with 22 to 25 ribs, generally 

 square or rectangular in section separated by flattened interspaces, the ribs 

 larger along the middle, smaller and crowded on the sides, both ribs and 

 interspaces crossed by fine, raised concentric threads. Cardinal area small, 

 triangular surmonted by the small beaks placed slightly posterior of the 

 mid-point. Internal margin coarsely furrowed in the middle zone, the 

 marginal furrows small or absent. Coloration white, irregularly splotched 

 with brown, or entirely ashy white with a brownish cast. 



Length 29.4 mm., height 30 mm., semidiameter 9 mm. Left valve, 

 Zorritos. 



T. tessellata and T. strigilata were described by Sowerby at the same 

 time and on the same page, the former placed first; both seem to represent 

 variations of each other, T, strigilata is the commonest and most typical 

 form, for that reason I have given it precedence over the other. T. strigilata 

 appears closely related to T. arata Conrad from the Miocene of North 

 Carolina. Pectunculus pectenoides Deshayes from Panama is perhaps equiv- 

 alent. 



Range — Lower California to northern Peru. Ecuador: Manta, Santa 

 Elena. Peru: Zorritos. 



Tucetona strigilata canoa (Pilsbry and Olsson) 



Glycymeris canoa Pilsbry and Olsson, 1941, Proc. Acad. Nat. Sci. Philadelphia, vol. 



93, p. 54, pi. 13, figs. 2, 2a Pliocene, Punta Blanca, Ecuador. 

 Glycymeris (Tuceta) tessellata canoa Pilsbry and Olsson, Hertlein and Strong, 1943, 



Zoologica, vol. 28, pt. 3, p. 152. 



This form was first described as a fossil from the Pliocene of Ecuador. 

 It has been reported from the Recent fauna by Hertlein and Strong who 

 considered it as a giant form or subspecies of T. tessellata. According to 

 these authors, it differs from T. tessellata (strigilata) by its much larger 

 size, extremely broad ribs, and in that the color markings are arranged in 

 concentric zigzag lines rather than in the shape of large spots. 



Range — Gulf of California and perhaps southward to Ecuador. Known 

 living only at Arena Bank, in the southern end of the Gulf of California 

 (Hertlein and Strong). 



Subgenus AXOACTLS Morch, 1861 



Type species by subsequent designation, Hertlein and Strong, 1943, 

 Axinaea (Axinactis) inaequalis (Sowerby). 



Shell solid, rounded to obliquely subtrigonal or cardiform, the umbones 



