NO. 1237. SYNOPSIS OF THE LUCINACEA—DALL. 791 



THYASIRA (AXINULUS) FERRUGINOSA Forbes (as Kellia), 1844. 



Aleutian Islands in 00 fathoms; Krause. 

 See the Atlantic list for further data. 



AXINOPSIS VIRIDIS Dall, 1901. 



Plover Bay, Bering Strait, southward to Catalina Island, California, 

 on the east, and to northern Japan (Capt. St. John, R. N.) on the 

 west, in 5 to 167 fathoms. 



A silky green, solid, orbicular species with very distincth^ developed 

 cardinal teeth. See notes and descriptions. 



AXINOPSIS SERICATUS Carpenter (as Cryptodon), 1864. 



Kyska Island, Aleutians, south to Puget Sound and Catalina Island, 

 California, in 2 to 120 fathoms. 



More ovate, flatter and thinner, with a less developed dentition and 

 pale yellow periostracum. The name was misprinted sei^ricatus in the 

 British Association Report of 1863. See notes and descriptions. 



Family DIPLODONTID.E Dall. 



This family is composed of Lucinoid shells, in which the external 

 limb of the gills is developed, reflected, and sometimes appendiculate, 

 the adductor scars not projecting into the disks of the mantle, the 

 hinge with the laterals obscure or absent, the valve margins plain, the 

 shell suborbicular in outline, rarely nestling and irregular. The foot 

 is elongated, cordlike, and more or less distally clavate in the tj^pical 

 forms, but may be nearly normal in the estuarine Joannisiella^ afford- 

 ing a parallel to Jagonki in the Lucinidre. Thoughout the family the 



dental formula is ^ ' ' :^, the central cardinals being usuallv bifid. 

 R 0.0101.0 



The fossil genus S])hcerk)la has much the appearance externally of 



Dlj)lodo)ita^ but the shell is heavy, and the hinge edentulous, and its 



relations to this family remain to be made out. The genus Taras 



Risso, from the figure and description,^ would seem to be a Dlplo- 



donta^ in which the delicate posterior cardinal of the left valve had 



been broken away and the corresponding tooth of the right valve 



mistaken for an adjacent lateral. It was founded on T. antiquatus 



Risso, a fossil of La Trinite (Tertiar}^). If this identification proves 



correct, the name Taras will supersede Dlplodonta^ being five years 



earlier in date. It was placed next to Lorvpes by Risso. I do not 



make the substitution, hoping that some Italian naturalist may be able 



to examine Risso's type species, and thus arrive at certainty before 



upsetting an old and familiar name. 



1 Hist. Nat. Eur. M^r., IV, 1826, p. 344, pi. xii, lig. 167. 



