332 APPENDIX. 



anfractus quatuor obtuse angulatos exhibente ; latere dextro excavate, anfractus duos cum 

 dimidio cstendente ; apertura ovato-triangularis, interdum utroque valde expansa. PI. XI, 

 figures 12, 13, 14, 15, 16, IT, and 18. 



Shell discoidal, attaining a large size, delicately striated, of a watery-wbite color ; when laid 

 upon the right side the shell has a remarkable conical or dome-shaped aspect, the extreme 

 periphery being in a plane with the right side or base, from which the whorl grapually slopes 

 upwards, terminating at the summit in a broad and deep concavity, exhibiting four well-marked, 

 obtusely angulated whorls ; the right side is decidedly concave, exhibiting two and a half or three 

 well-rounded volutions. Aperture ovate-triangular, in middle-sized specimens projecting about 

 equally to either side, in small specimens projecting to the right side only, and in the largest, 

 spreading amply to both sides, and especially the right, where it expands and forms a remarkable 

 ear-shaped aperture. 



Diameter of the disk, in the middle-sized specimens, five-eighths of an inch, and in the 

 largest, one inch ; axial diameter of the first, one fourth of an inch, of the latter, half an inch ; 

 and in one specimen the breadth of the aperture, from side to side, is five-eighths of an inch. 



Locality. Found in the Colorado Desert ; and also by Dr. Webb. 



I have associated specimens differing greatly in size and in developement of the aperture, but 

 all agreeing in the peculiar slope of the outer volution, giving a conical outline when lying on 

 the side. The fully developed specimens have the general aspect of P. corpulentus, Say ; but 

 besides the form of the volution and the consequent shape of the aperture, that shell is more 

 coarsely striated, the whorls on the right side lie nearly in the same place, and on the left side 

 but two whorls appear. It differs from P. trivolvis, Say, in nearly the same particulars. In 

 external surface it is more like P. glabratus, Say. 



AMNICOLA PROTEA, Gould. 

 [ Proceed. Bost. Soc. Nat. Hist. , V. 129. Mar. 1855.] 



T. parva, elongata, gracilis, variabilis ; anfractibus 7-8 convexis, profunde discretis, sim- 

 plicibus, vel filis volventibus et costis longitudinalibus varie ornatis et clathratis : apertura 

 ovata ; labro continue, simplici, anfractum penultimum vix attigente. PI. XI, figures, 6, 7, 

 8, and 9. 



Shell small, turreted, slender, greatly elongated, chalky-white, (so far as seen,) variously 

 proportioned, composed of seven or eight whorls, which are either convexly rounded or broadly 

 shouldered, and separated by a deep suture the surface either smooth throughout, or more 

 frequently sculptured with revolving threads or longitudinal ribs or decussated by both in 

 various proportions, the upper whorls being in nearly every instance decussated ; aperture ovate, 

 lip simple, continuous, generally detached from, or scarcely appressed to the penultimate whorl, 

 in many instances leaving an umbilical chink. 



Largest specimens three-tenths of an -inch long and half an inch broad. 



Found in the Colorado Desert ; also by Dr. T. H. Webb. 



This species is peculiar on account of its elongated, slender form, and differs from the other 

 species of the genus yet described in being variously sculptured with revolving ridges and 

 longitudinal folds, like many of the Melaniae. It varies greatly also in its relative proportions 

 of length and breadth. It is as slender as A. attenuata, Haldeman, and much larger. [This 

 appears to be the same shell as that subsequently described by Mr. Conrad, under the name of 

 Mdania exlgua.] 



