46f5 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



tate terminal branches, with two smaller oppositely -arranged lateral branch- 

 lets on each side; second lateral sinus as long as the first, but narrower, and 

 *a i a similarly divided, excepting that its 



^ r jS ^A %lj a £ larger terminal branch is on the si- 



ra 2 phonal side; second lateral lobe about 



t is S one-third longer than the first, which 



a £ it does not quite equal in breadth, 



| ~ provided with three or tour rather 



s t short, more or less sinuous and 



- ,3 



? - -a digitate, alternately-arranged, lateral 



_> 



branches on each side, and a larger 



~J->^^3 g JS terminal division with five small sinu- 



mgLyJ "' ~ - i -5° ous branchlets ; third lateral sinus of 



. ■■ « » 



' ' rX^;J •"- . vv"> ^ -g g very nearly the same size and form 



?, ^3 -"■/ i "J r " : ;* " i i t as the second ; third lateral lobe about 



.' '' -im,i MsM one-fourth larger than the second, 



r8*«^Si^k 2 ° "g and nearly similar in its details ; suc- 



i ■■,,: \ i~^ : ? x$-f. a° I ceeding lateral sinuses gradually di- 



« - j - C^?u = 2*5 £ minishing in size and complexity to- 



ts — oiS-vX;^ a ~ c 



|j> j"\ > " i^J, wavd the umbilical margin, all bifur- 



■*G ..-'■>'* s°l eating at the end excepting the eighth 



^5^,r = ^t and tenth, which are tripartite, and 



L *3|a ^* i-a-S the eleventh and twelfth, which are 



-^I^JfiMF- ~ § a merely trilobate; fourth lateral lobe 



- cr„-i >vfe I c ^ about half as large as the third, but 



s rv^s^ fit, @.» .~ .n ^ 



1 '■'-,-'' > *, = I * I similar in its details, while the sue- 



to O w 



§ 3 "t ceedingonesbecomegraduallysmaller 

 2 'S o toward the umbilicus, and all show 



§ ja tt 



§ a a a more or less tendency to a tripar- 



8 o 



l-S =. tite arrangement of their terminal 



« ° s 



^s 2 branches, excepting the very small 



.-H M 43 



£•§,.5 twelfth one, which is merely oh- 



o* -r s 



| J§ J scurely bilobed, or nearly simple. 

 I I » In comparing the annexed cut and 

 "* % I the foregoing description of a septum 

 ■I I of this shell with the septa of other 

 specimens of the species, it should be remembered that it was made out 



