WHITEAVES.] LARAMIE AND CRETACEiJCS IX VERTEBRATA, 15 



the maximum breadth : outer whorl, as mea-ured clo>e to the aperture, 

 a little longer than the sj^ire. Vnlution- ^ix or -even, the fir^t three or 

 four slender and increasing slowly in -ize. the two next, c-peeially the 

 last but one, increasing rapidlj' both in length and breadth, each being 

 obliquely and very gently convex : suture well defined but not very 

 deeply impressed : outer whorl moderately convex, about one-third 

 longer than broad, and broadest a little above the middle. Aperture 

 rather more than one half the entire length of the shell, a little 

 more than twice as long as wide, nan-owly subovate or semiovate, 

 contracted and acutely angular above, broader and usually more 

 rounded but in some specimens bluntly pointed below ■ outer lip thin 

 and simple : columella bearing a narrow, prominent and oblique fold 

 near its base, the fold in some specimens being bordered below with a 

 rather deep gi-oovo : columellar callus broad and closely adherent, 

 except at its extreme base, where it is slightly separated from the main 

 body of the shell in such a way as to form a minute and narrow kind 

 of umbilical chink or perforation. 



Surface nearly smooth, marked only with the faint and somewhat 

 distant lines of growth common to most species of this genu^. 



Length of a large and nearly perfect specimen, fifty-three milli- 

 metres : maximum breadth of the same, twenty-two mm. : length of 

 body whorl, as measured close to the outer lip, thirty mm. In a slightly 

 smaller ■^pecimen which shows the characters of the aperture bettei', 

 the length of the aperture is twent3'-five mm. and its maximum width 

 only ten. 



Pincher Creek, cro-sing of Mill Creek and Fort MacLeod Trail, very 

 abundant, G. M. Dawson and E. G. McConnell, ISSl, and T, C. Weston, 

 188.3. Goo^ebeny Canon, St. Mary Eiver, frequent, G. M. Dawson, 

 1881 : Second or Xorth Bj-anch of the Milk Eiver, G. M. Dawson, ISSl. 

 All from the St. Mary E. Series. 



During the p)a.^t four j-ears upwards of two hundred specimens of 

 one or more specie^ of Physa, whose relations to forms already 

 described are extremely puzzling, have been collected by ofllcers of the 

 Survey in the Laramie Formation of the Canadian ;N"orthwest. Out of 

 these specimens it is possible to select a few which have a large and 

 long body whorl, and a very short acutely acuminate spire, and these 

 cannot at present be distinguished fj-om the Fhysa Copei of White. 



By far the larger number, however, whose characters are more min- 

 utely described above, have a much longer spire, though it apparently 

 never ciuite equals the outer whorl in length. Such specimens ^eeni to 

 be very nearly related to the Bulinus disjunctus of White, and have been 

 doubtfully referred to that species in Dr. Dawson's report, though in 

 JB. disjunctus the length of the spire is said to be " a little more than 



