2 DR. P. P. CARPENTER ON NEW MOLLUSCA. 



obtain an adult shell, which passed into the Cumingian Collection 

 Having removed the animal matter with great care, the loop was 

 found to retain the form seen in the young shell, only perhaps siil 

 more open. This is the first recent species of the genus which lias 

 been discovered with a sculptured surface, and affords an instructive 

 lesson not to rely on external characters. 



Teretratula unguicula: 1, 2, outside views of Mr. Cuming's adult specimen, 

 natural size : 3, 4, inside views of the upper valve, slightly magnified. 



The outline of the adult is much rounder, and the margin blunter, 

 than in T. caput-serpentis. Inside, the noncompletion of the some- 

 what (U-shaped loop is a very obvious character. This is large ir 

 proportion, extending to about two-fifths of the length and one- 

 tliird of the greatest breadth of the shell. It is bent upwards in the 

 middle, as seen from the partly opened valves ; with a double wave at 

 the sides, as seen from the direction of the opposite valve. Two spurs 

 ascend from the crests of the side waves, as though preparing tc 

 complete the loop. The similar Terebratella angustata from Japiin, 

 when of the same size as Dr. Cooper's specimens, has the loop quite 

 continuous *. 



Subgenus NETTASTOMELLAf. 



Pholadidea : valvis postice in calycem iesiaeeum planatum prth 

 longatis ; calyce coriaceo nulla. 



Nettastomella darwinii, Shy. (diag. auct.). 



N. t. minore, elongata, tenuissima ; parte postica costis radian- 

 tibus acutioribus circ. vii. et laminis concentricis acutissimis^ 

 distantibus, antice continuis, elegantissime ornata; rostris pla 



* Dr. Cooper having forwarded for my inspection a large aud beautifully prr 

 feet specimen of the true Waldheimia californica, I have compared it with the 

 series of the very variable TV. glohosa in tlie Smithsonian Museum, undoubtedly 

 from Orange Harbour. The California shell, however, has a strong browuish- 

 red tinge, and does not display the beautiful veining of the Maghellau species. 



t Th. vriTTa, a duck, trro/jn, mouth. The name Netastoma, given in the 

 ' Brit. Assoc. Report.' 1863, being preoccupied in another subUngdom, accoidinj 

 to Dr, Cooper, it is thought necessary to \ary the termination. 



250 



