10(3 THE VOYAGE OF H.M.S. CHALLENGER. 



Dr. Grwyn Jeffreys has shown that this species ranges from the north of England to 

 the Mediterranean and Madeira, and is found fossil in the Coralline Crag and Sub- 

 appenine Tertiaries. A fact in connection with this species which, I believe, has not 

 Ijeen previously recorded, is the presence of a small internal ligament. This is especially 

 noticeable in young shells, and is placed oblitpely, as in the genus Scmele, behind the 

 cardinal teeth. Several other species also possess this feature, and among those 

 obtained by the Challenger Expedition may he mentioned Tellina tenuilirata, Sowerby, 

 Tellina diluta, n. sp., Tellina Jijiensis, Sowerby, Tellina casta, Hanley, Tellina languida, 

 n. sp., and Tellina tenuilamellata, n. sp. Two other species also have a portion of the 

 ligament internal, but located, not obhquely as in the above species, but immediately 

 beneath the beaks. These are Tellina semen of Hanley, and Tellina semitorta of Sowerby. 



Although these forms differ from others in the genus in this respect, I do not deem it 

 advisable to propose for them at present a new generic or subgeneric section. The grada- 

 tions in form and general aspect from one genus to another are so slight that I feel convinced 

 that a series of species of Tellinidse could easily be got together which would clearly represent 

 a gradual transition from group to group, so that it would be impossible to demonstrate 

 where, on the one hand, Tellina proper, without any internal ligament, ended, and, on the 

 contrary, where Seniele, with a conspicuous internal cartilage, commenced. Similar 

 gradations in respect of form, solidity, and dentition are also discoverable, so that it 

 becomes quite a simple matter to graduate the forms of Ahra into the genus Semele. 



Tellina ( ?) tenuilirata, Sowerby. 



Tellina tenuilirata, Sowerby, Coccb. Icon., vol. xvii. fig. 219, a, b {non sp. 253). 

 Tellinu tenuilirata, Angas, Proc. Zool. See. Loud., 1867, p. 919. 



Testa parva, alba (interdum rosea), concentrice tenuiter striata, valde insequilateralis, 

 oblonga, postice acuminata, antice acute rotundata. Margo dorsi anticus elongatus, 

 rectiusculus, vix descendens, posticus longe brevior, valde obliquus, subrectilinearis. 

 Margo ventralis leviter curvatus, postice levissime incurvatus. Umbones parvi, acuti, 

 circiter in -g- longitudinis siti. Dentes cardinales duo inajquales in valva dextra, 

 unicus triangularis in sinistra ; laterales elongati, graciles. Ligamentum internum 

 angustissimum, valde obliquum. 



This species is moderately thin, white or pink, small, and sculptured with fine con- 

 centric lines of growth. It is nearly twice as long as high, very inequilateral, the small 

 acute beaks being located at about one-third of the entire length from the hinder 

 extremity. The anterior portion narrows slightly and is sharply rounded at the end, 

 the posterior side being much more acuminated and somewhat wedge-shaped. The front 

 dorsal margin is elongate, only a little oblique and straightish, the posterior much 



