1890.] MARINE MOLLUSCA OF ST. HELENA. 303 



'Challenger' Lamellibianchiata, p. 1(51. It has not previously 

 been met with so far south in the eastern parts oi' the Atlantic. 



RocELLARiA DUBiA (Peuiiant). 



Hab. Mediterranean, Red Sea, North Sea, Madeira, Canary 

 Islands, Cape Verde Islands. 



St. Helena is, I believe, the most southern locality known for this 

 species. 



Chama, sp. 



Several specimens of a species of this genus were collected by 

 Capt. Turton. The young examples exliibit short spines on both 

 valves, but the adult shells are too worn to be determined. The 

 interior is white, more or less stained with brown, especially towards 

 the margins. Length of largest specimen 75 millim. 



C. gryphoides, Linn., appears in Jeifreys's and Melliss's lists of 

 St. Helena shells. I have not seen the specimens which they exa- 

 mined, but doubtless they belonged to the same species as those 

 collected by Capt. Turton. It is probable that they are correctly 

 identified, but in such a difficult group as Chama one hesitates to 

 pronounce a positive opinion without a special study. 



Basterotia oblonga. (Plate XXII. figs. 5, 5 a.) 



Testa ohlongo-subquadrata, valde huequilateralis, albida, coiicen- 

 trice striata ; valvce cequales, ah umbone ad extremitatem posti- 

 cam obtuse anrpdatce ; margo dorsi posticus fere rectus, ventralis 

 subrectilinearis, vel in medio leviter incurvatus ; latus niiticuui 

 breve, obliquum, inferne rotundatum, posticum oblique curvaluiii, 

 ad extremitatem acute rotundatum ; winhones parvi, acuti, ante- 

 mediani, cirdter ini- longitudiais siti ; dens car din alis in utraque 

 valva prominens, acutus ; pagina interna nitida ; cicatrices bene 

 im^yressce. 

 Longit. 8| millim., alt. 5, diam. 4g. 



This is a more oblong species than B. carinata or B. gouldii and 

 some others. 



This group of shells was first recognized by Gray in 1842 

 (Synopsis Contents Brit. Mus. p. 78) and named Harlea. His de- 

 scription runs thus: — "The Harlea are oblong, subquadrate, thin 

 shells, with a sharp keel from the umbo, and conical hinge-teeth." 



This diagnosis applies perfectly to the type marked by Gray him- 

 self as Harlea, and this was described the year following (1843) by 

 Hinds as Corhula qiiadrata. This species also forms the type of 

 Recluz's genus i^McAftm (1850), and Homes in 1859 described a 

 fossil species belonging to the same group under the generic name 

 Basterotia. Considering the imperfection of Gray's description, 

 and the fact of his not citing any species, I think it would be ad- 

 visable to ignore his genus Harlea, although, personally, I am sure 

 what group he intended to include under that name. 



A genus Eucharis having been published by Latreille in 1804, 

 this name cannot be employed for the present group of sliells. We 



21* 



