1919.] NATURAL SCIENCES OF PHILADELPHIA. 201 



Remarks. — Despite its great size, 0. c. apiarium is nearer, I think, 

 to 0. c. limitaris (Dawson) than to any of the other described races 

 of the cooperi complex. The latter differs in its very much smaller 

 size, less elevation, rather greater carination of the front part of 

 the last whorl, and very much weaker spiral striation on the upper 

 /portion of the whorls. Relative to the size of the shell the hnes of 

 growth are coarser in Iwiiiaris, and the adult shell has from | to 

 f of a whorl less. 



Limitaris has long been greatly misunderstood, and for a time 

 I thought the Glacier Park race might prove to be identical with it, 

 but the recent receipt of good comparative material from the type 

 locality of limitaris, through the kindness of Mr. Frits Johansen, of 

 the Geological Sm-vey of Canada, has led me to the conclusion that 

 the two are measurably distinct, though limitaris comes from near 

 Waterton Lake, just over the border from Glacier Park, Montana. 



If these conclusions are correct, both apiarium and limitaris will 

 stand as reasonably well differentiated subspecies of 0. cooperi (Bin- 

 ney). The McDonald Creek Canyon shells are among the most 

 elevated and largest cooperi I have seen, being surpassed in bulk 

 only by Pilsbry's 0. c. maxima from the Yellowstone National Park. 

 Maxima further differs in its more depressed contour and much 

 more capacious umbilicus. For the loan of a specimen of maxima 

 permitting my direct comparison of the two I am indebted to Dr. 

 Pilsbry. 



Another shell which is probably quite close is that represented 

 by the three largest figures given by Elrod in his "Biological Recon- 

 naissance in the vicinity of Flathead Lake" (;02, pi. 27), over the 

 name of Pyramidula strigosa, var. They are from McDonald Lake, 

 Mission Mountains, Montana, which should not be confused with 

 the lake of the same name in Glacier Park near the type locality of 

 apiariu7n. Not any of the shells he figures on the plate cited appear 

 to me to be correctly referred to strigosa. 



Most of the living specimens taken were found to contain unborn 

 young. The number of embryos per adult varied so greatly that 

 it is evident the smaller numbers did not represent entire broods, 

 probably the last members of a clutch in progress of birth. Twenty 

 specimens from Station XV yielded from 2 to 18 embryos each, 

 the average being 11.6. At Station XVI 12 specimens yielded from 

 3 to 23 embryos each, the average being 14.5. Where but few em- 

 bryos were found they proved generally to be above the average 

 in size, which accords with the supposition that in such cases par- 

 turition was more advanced. 

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