208 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



Genus LUNARGA Gray 1842 



Lunarca Gray, Synopsis of the Contents of the British Museum, ed. 44, 



1842, p. 81. 

 Syn.: Argina Gray 1840 {nomen nudum). 



ArginaGray 1842 (non Hiibner 1822). 

 Arginarca McLean 1951 (new name for Argina Gray). 

 Type of genus: Lunarca costata Gray 1842 (by monotypy) = ovalis 



(Bruguiere) 1892 = campechiensis (Gmelin) 1791 =pexata (Say) 



1822 = arnericana (Wood) 1828, etc. 

 Remarks: The anterior teeth are irregular and have a tendency to grow 

 together in larger specimens, and a groove may be formed in the opposite 

 valve for the reception of these confluent teeth. Gray's specimen, upon 

 vv^hich Lunarca was based, is probably an extreme case in which the 

 anterior teeth had grown together as one. There can scarcely be any 

 doubt that Lunarca costata, known from only one specimen, is the same 

 as Lunarca ovalis (Bruguiere) (see figures given by H. and A. Adams 

 (1857), PI. 125, figs. 7, 7a, L. pexata (Say) ; L. costata Gray, figs. 8, 

 8a) 



Four species belonging to this group are described from the west 

 coast of America. They are: Lunarca hrevtfrons (Sowerby) 1833, 

 Lunarca vespertina (Morch) 1861, Lunarca brevifrons hucaruana 

 (Sheldon and Maury) in Maury, 1922 (described as a variety of L. 

 brevifrons), and Lunarca melanoderma (Pilsbry and Lowe) 1932. 

 However, none of these species seem to be clearly circumscribed ; the 

 number of ribs has mainly been used to identify them. Lunarca brevi- 

 frons seems to have been reported only two times ; from Tumbes, Peru, 

 where the type specimen was found, and from Mazatlan, IVIexico, from 

 which locality Carpenter (1856a) reported it in the Reigen Catalogue, 

 with a question as to its identity. Maury (1922) and Hertlein and 

 Strong (1943) say that L. brevifrons is distinguished by having only 22 

 or 23 ribs, while the other species of the group have more than 30. 

 Sowerby (1833) gives no number of ribs in the description of the type; 

 but Reeve (1843) gives the number as 22 or 23 in his description of 

 L. brevifrons. However, as his figure of this species seems to have far 

 more than 22 or 23 ribs, his recording may perhaps be an error for 32 

 or 33. An examination of the type material is necessary to settle this 

 question. 



The status of the three other species is also questionable. Hertlein 

 and Strong (1943) suggested that L. melanoderma might be the same 

 as L. brevifrons bucaruana. L. vespertina (Morch) is described from 



