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



o^)taia an adult shell, wiiich 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 perliaps stil' 

 more 0|)en. This is the first recent species of the genus which has 

 been discovered with a sculptured surface, and affords an instructive 

 lesson not to rely on external characters. 



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

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



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

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

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

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

 third 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 Japan, 

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

 continuous *. 



Subgenus NEXXASTOMELLAf. 



Pholadidea : valvis postice in calycem testaceum planatum pro* 

 longatis ; calyce coriaceo nulla. 



Nexxasxomella darwinii, Sby. (diag. auct.). 



N. t. minore, elongata, tenidssima ; parte postica cnstis radian* 



fAbus acufiorihus circ. vii. et laminis concentricis acutissimis; 



distantibus, ant ice confinuis, elegantissiiae ornata; rostris pla^ 



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

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

 %eries of the very variable W. glohosa in the Smithsonian Museum, undoubtedly 

 from Orauge Harbour. The Calitoriiia shell, however, bus a strong browuish- 

 red tiuge, and does not display the beautiful veiuing of the Maghellan species. 



t Th. vriTTa, a duck, aroixa, mouth. The name Netastoma, given in the 

 ' Brit. Assoc. Report,' 1865, being preoccupied in another subkiugdom, according 

 to Dr. Cooper, it is thought neccsaary to »ary the teruiinutiou. 



250 



