NO. 2 



ROST : THE FAMILY ARCIDAE 



209 



one single broken valve 7.75 mm in length, from Realejo, Nicaragua. 

 Three samples of small specimens from Baja California and the Gulf of 

 California are here referred to L. vespertine (Morch), as his description 

 fits them very closelj^ One sample from Panama and two from the 

 Galapagos Islands are referred to Lunarca sp. 



It is quite possible that all Lunarca from the west coast is one vari- 

 able species similar to Lunarca ovalis from the east coast. A large 

 amount of material from many localities is needed before further con- 

 clusions can be drawn. 



Lunarca vespertina (Morch) 1861 



PI. 15, figs. 24 a-b; text-figs. 93 a-c 



Area (Argina) vespertina Morch, Malakozool. Blatter, vol. 7, 1861, 



p. 204. 

 Fig.: Hertlein and Strong, 1943, PI. 1, figs. 6-7. 

 Type loc: Realejo, Nicaragua. 

 Holotype: ? 



Remarks: The west American species belonging to this genus are dis- 

 cussed in the previous section under the genus Lunarca. 



Four specimens are here referred to Lunarca vespertina. They are 

 all small and fit Morch's description very closely. The only figure of 

 this species in existence is given by Hertlein and Strong (1943, PI. 1, 

 figs. 6-7) and the rather large specimen figured, 36.1 mm in length, 

 does not strongly resemble the shells referred to the same species in the 

 material at hand. The authors state, however, that larger specimens 

 become more elongate, while the younger ones are more quadrate in 

 shape. 



y Wv- 



c r 



Fig. 93. Lunarca vespertina (Morch) 1861. Off Punta Pequefia, 

 Baja California, a. Lateral view. b. Dorsal view. c. Ab- 

 dominal sense organs. Length, 17.5 mm. 



