12G 



Bab. — Philippine Islands, Van Dieman's Land, East Indies. 



Coll. Acad. Nat. Sciences. 



Description. — Valves wanting. Tube contorted somewhat, gradually in- 

 creasing in diameter to the base, and growing to the length of three feet. 

 The siphonal end is divided into two internal tubes by a transverse partition. 

 External surface roughened, by its contact during growth with surrounding 

 objects, and exhibiting impressions of pebbles, shells, &c. Diameter at base 

 one and a half inch inches, at siphonal end, three-quarters inch. Base 

 rounded, "closed by two overlapping, convex septa, arising from the sides 

 and completely closing the ends. The tube is thickened above as the animal 

 leaves it, and is much thinner near the lower or closed extremity,"* just aroand 

 which are scattered small perforations for the admission of water to the 

 animal. 



Pallets about one inch or more in length, the stalk gradually increasing 

 into a triangular blade, the end of which is truncate ou one side and two- 

 horned on the other side. 



i'rom Proceedings of the Academy of Natural Sciences of Philadelphia, September, 1882. 



Description of a new Genus and Species of PHOLADID.ZE. 



BY GEO. W. TRYON, JR. 



Subfamily JOUANNETIN^, Tryon, 1862. 



Diplothyra, Tyron. 



Shell with a double accessory valve ; the principal plate placed directly over 



the umbones, with a smaller anterior one adjoining. 



This genu3 is allied to Martesia ; but differs in the double or divided doreal 

 valve. 

 D. Smithii, Tryon. 



Testa brevi, ovata, in medio oblique divisa, antice acute striata, 

 postice paulo striata vel laevigata; lamina umbonali ovata, posticfe 

 subtruncata, antice rotundata, lamina anteriori parva, antice sub- 

 acuminata. 



Shell short, ovate, divided in the middle by an oblique impressed 

 line, posterior to which the surface is covered with growth lines 

 only, but anteriorly it is finely and sharply transversely sculptured, 

 and obsoletely radiately ribbed in some specimens. 



The umbonal plates are generally much distorted, so that no particular form 

 can be traced throughout alt the specimens, though the more perfect approach 

 to that depicted in the magnified figure above. 



Length -6 ; height and breadth -4 inch. 

 r Collections of Acad. Nat. Sci., Smithsonian Institution, Sanderson Smith, 

 New York ; Hugh Cumming, London; Geo. W. Tryon, Jr. 



Habitat. — Tottenville, Staten Island, burrowing in oyster shells. 

 Mr. Smith, to whom I am indebted for the opportunity of examining numer- 

 ous individuals of this curious species, gives the following interesting iafor- 

 mation in relation to them : 



;< The shells were all dead, and I have found as yet no positive evidence of 

 the oysters being imported ones, although from the great number of southern 

 oysters planted in Prince's Bay and the neighborhood, there is a considerable 

 probability of this. The large number of oyster shells which have been 

 bored from the inside, and consequently after the death of the oyster, suffices 

 to show that the shell is now, or very recently has been living here, as it in 

 hardly likely that so many large dead shells would have been accidentally 



* Gray, Zool. Proc. part 25. 



