96 MAZATLAN BIVALVES 



A puzzling little shell, of which were found only one minute 

 valve and a larger fragment. R r markable for the very stout 

 ribs, well armed with coarse tubercles, and for the Lucina-like 

 shape of the dorsal margin. It has about 10 ventral ribs, but 

 the species probably has more when adult. If then of the 

 same shape, it may take the name of C. lucinoides. Long. '04, 

 lat. "04, alt. '03. 



Hob. Mazatlan ; extremely rare ; in shell washings ; L'pool 

 Col. 



Tablet 463 contains the valve. 



FAMILY LUCINID^E. 



GENUS LUCHSTA, Brug. 



This genus, so abundant in the Atlantic, and especially in 

 the West Indies, appears very rare on the Pacific coast of 

 America. C. B. Adams records only one species from Panama, 

 and this does not belong to the genus ; D'Orbigny none from 

 the West coast of S. America. Reeve describes 3 species 

 (fibula, eburnea, and calculus) discovered by Mr. Cuming, be- 

 sides L. punctata and muricata, previously known ; and L. 

 annulata from ? California. Dr. Gould has another, from 

 Acapulco. Only one small species was at all common in the 

 Mazatlan collection ; though there is evidence of the existence 

 of a tolerable number of others. Some of the Lucinse are not 

 at all constant in their characters ; the same species sometimes 

 displaying, or not, radiating and concentric ribs, and having 

 its margins smooth or crenated. Not a few of the species 

 appear to have a very wide distribution ; L. occidentalis, Rve. 

 (olim pecten) being quoted from the West Indies and Ld. 

 Hood's Island, and L. borealis from the British Seas and the 

 Philippines. Many of the Mazatlan species were found en- 

 tangled in the byssal mass of the large Modiolse. * 



136. LUCINA (CODAZIA) TIGEKINA, Lin. 



Venus tigerina, Linn. Syst. Nat. p. 1133-4. Bom Mus. p. 70. 

 Ckemn. vii. p. 6, t. 37, f. 390-1. Schroeter Mnl. iii. p. 136. 

 Mont. Test. Br. p. 119, t. 4, f. 1 Dorset Cat. p. 35, t. 1. 

 f. U.DiUw. Cat. vol. i. p. 191, no. 76 : Sfc. 



Cytherea tigerina, Lam. An. s. Vert. ed. 2, vol. 6, p. 318. 

 Turt. Dyth. Br. p. 164, pi. 10, f. 12. Flem. Br. An. p. 445. 



