Descriptions of New Fluviatile Shells. Ill 



Obs. — But a single specimen of this species is before me, but 

 it differs so much from all others that I cannot hesitate to place 

 it among well established species. M. acuto-carinata Lea is the 

 only one with which it may be compared, but that species has 

 the carina obsolete on the body whorl, the very point where it 

 is most remarkably developed in this ; the whorls also in the 

 M. torulosa diminish much more rapidly to an acute apex, 

 which in M. acuto-carinata is said to be obtusely elevated ; the 

 M. torulosa is remarkable for its acute elevation from the 

 broad base of the carina on the body whorl. In the columella 

 too of the present species there is no indentation, while in 31. 

 acuto-carinata it is "remarkably indented." 



31. Melsmia planogyra. 



Plate III. Fig. 11. 



T. elongato-conica, subglabra, crassa, fusco-virente ; spira valde 

 autem obtuse elevata ; anfr. 10-11, subconcavis, costa supra suturam 

 decurrente marginatis, et fascia fusca juxta costara ornatis ; anfr. ultimo 

 fascia altera infra angulum decurrente ; suturis impressis ; apertura 

 parva, rhomboidea, intus bifasciata ; labro valde sinuoso ; columella 

 recta, in sinum latum producta. 



Shell conical, rather smooth, thick ; of a dull, dark, horn- 

 color, unrelieved by any other except a rather indistinct, brown 

 band, revolving near the base of each whorl, immediately be- 

 low which a raised, rounded, subcrenulated ridge revolves 

 between it and the suture below ; spire much, but not acutely, 

 elevated, with a nearly rectilinear outline ; whorls 10-11, flat 

 or concave, and with a well impressed, channelled suture ; 

 aperture small, rhomboidal, diaphanous, exhibiting the dark 

 band of the exterior through its substance very faintly, far 

 within. Columella deeply curved, not indented, thickened at 



