104 MAZATLAN BIVALVES 



nitens, (Is. Muerte, 11 fm., sandy mud, Cuming,) L. tellinoides, 

 (do. Cuming : Taboga, not common, C. B. Adams,) and the 

 following, are placed by Woodward under Diplodonta (Man. 

 MoU. pt. 2, p. 298.) They differ essentially in form and habit 

 from the typical species of that remarkable genus, and have 

 relations (except in the hinge teeth) with Cyrenoides : but 

 until the animal has been examined, it would be presumptuous 

 to create a fresh one for their reception. 



152. ? DIPLODONTA SEKRICATA, Reeve. 



Lucina serricata, Conch. Ic. pi. 9, f. 25. 

 Cyrenoida serricata, P. P. C. Cat. Prov. 



Mr. Reeve tells us that this shell differs from the others 

 essentially in form ; but his descriptions and figures often 

 oblige students to take many things on trust. It has much the 

 appearance of a brackish water shell, having a glossy epidermis 

 eroded near the beaks. The allied species are however strictly 

 marine ; and even these (though very rarely) are pierced by 

 Gasteropods. The shell is extremely thin, Cyrenoides -shaped, 

 but with the teeth of Diplodonta. Muscular scars elongated, 

 rather irregular, The form is generally elongated, but some- 

 times nearly round ; beaks appressed ; ligament subinternal. 



The largest specimen measures long. '87, lat. '81, alt. '36. 



A rounded '72, '73, '31. 



Sab. Mazatlan ; not uncommon ; IS pool Col. 



Tablet 483 contains a minute pair, broken, measuring '07 

 across and 2 minute opposite valves, '03 across, from the Spon- 

 dylus washings, which probably belong to this species. If so, 

 they establish its marine station. The youngest valves, by 

 transmitted light, display a fine radiating fibrous structure. 



Tablet 484 contains 6 specimens, varying in age and shape. 



FAMILY KELLIAD^E. 



The little shells, either overlooked in the days of Lam. or 

 included in the heterogeneous genera Erycina and Amphi- 

 desma, are now found to be inhabited by animals greatly dif- 

 fering from each other. The British members, which alone 

 have been carefully studied malacologically, are distributed 

 by Clark (Moll. Test. Mar. Brit. pp. 88 et seq.) under the 

 families Kelliadse, Montacutidse, Turtoniadse, Arcadse & Ana- 



