90 THE VOYAGE OF H.M.S. CHALLENGER. 



Adams, wlio iiiakL' no meutiou of lateral teeth. These are very thin in this species, and 

 rather close to the beaks, especially the front one. In the right valve they are separated 

 from the dorsal line liy a narrow groove which receives the elevated marginal teeth of the 

 opposite valve. Indeed I fail to perceive hardly any difi'erence between the genus Thcora 

 and Abra, except that the cartilage-pit may be rather larger in most species of the former 

 than in any forms of Ahra with which I am acquainted. The form and texture of the 

 shell are similar in both groups, and the pallial sinus is likewise large and deep. In the 

 Annals and Magazine of Natural History for 1864, vol. xiii. p. 208, Mr. A. Adams 

 again characterises Theora, stating that there are no primary teeth, and in describing 

 Theora (NecBva) fragilis (Proc. Zool. Soc. Lond., 1855, p. 226) he observes that "there 

 are no lateral teeth." Such assertions as these show how very superficial his examination 

 (jf the sjjecies he cites must have been, for all have true cardinals as well as lateral teeth. 

 The subgenus Eridojolemu, which he founds on the Theora lumbrica of Gould, is not in 

 my opinion worthy of retentioii. It differs only from other forms of Theora in possess- 

 ing a radiating ridge or rib within tlie valves extending from the beaks obliquely towards 

 the anterior end. 



This genus (Theora) was formerly placed by the brothers Adams near NeoBva, but 

 afterwards was removed by A. Adams to the Telliuidae, a location which is probably 

 correct. He says " the deep sinus in the pallial line, together with the form of the 

 valves and the pellucid vitreous texture of the shell, clearly show that this genus belongs 

 to the Scrobiculariate division of the Tellinidse, and not very far from the Abra of 

 Leach or Sy)idos)iii/a of Reeluz." 



Family T E L l i n i n m. 



Subfamily Psamjiobiin.^. 

 Psammobia, Lamarck. 



Ps^ammobia ' costulata, Turton. 



Psammohia cosfulafa, Turton, Conch. Ins. Brit. Dithyra, p. 87, pi. vi. fig. 8. 



Psanimohia costulata, Brown, 111. Conch. Gt. Brit., pi. xxxi.K. fig. 34. 



Psammohia costulata, Philippi, Abbild., vol. i. p. 98, pi. i. figs. 3, 4. 



Psammohia costulata, Keeve, Conch. Icon., vol. s. fig. 38. 



Psammohia costulata, Forbes and Hanley, Brit, lloll., vol. i. p. 279, pi. xix. fig. 5. 



Psammohia costulata, Jeffreys, Brit. Conch., vol. ii. p. 394, vol. v. p. 187, pi. xlii. fig. 2. 



Psammohia discors, Philippi, Enum. Moll. Sicil., vol. i. p. 23, pi. iii. fig. 8. 



Habitat. — Tenerife, Canary Islands, at a depth of 70 fathoms. 



This species has already been recorded from these islands. It has a wide range, 



' The generic name Gari of Schumacher was published iu 1817, a year previous to Lamarck's Psammobia ; the 

 latter, however, being generally adopted, and more in accordance with the accepted notions of zoological nomenclature, 

 should, I think, be ineferred. 



