OSTUAOOI 



.! ) 



I'n.f. T. Rupert .bine- recently descrihed from Canada (ContH ' 



Mien. T;iL pt. :i. 1VI|>, that ma\ ' ic with tin ////./ 



/ and ls.-liilin<i lulu-limn, the latter appearing tn l>e much like /. In,. 



I.. 



I'l.XTI M.I I -i. 



,illl. 



. wide-t po-teriorl\. tumid, the puint of greatest thickness hut. 



little behind aii<l beneath the center: anterior outline semicircular; dorsuni >tr.tight, 

 nut angular in front, and quite ohtu-e Kehiml. po-ferior margin -omeu hat obliquely 

 ronnde-l. y truncated ab< .irthe ventral ed^eof the left valve a di>tinct 



channel <>r L f i'<'\''. deepest centrally. I -.->ted the name. Surface snumtli. 



Tin- . l<i-el\ related to /, . htmiiln 1'lrich, occupying: a similar ^eolo^ical 



position in Kentucky and Tennessee, and of which a ritfht valve i- li^urcd for com 



on mi plate J.'i. (tiL's. 1:5 !"). Tlic outline in that r i- not SO 



!arly rounded in front, nor ^n full antoro vent rally, the greatest convexity i- 

 more posterior and -carcely so great, ami the dorsal angles more distinct. Hut the 

 feature particularly relied on in di-tin^uMiin^r the two species is the groove aloii^' the 

 \entral l.order of the left valve in /.. i-iimili*. the Kentucky form l>eing without thi- 



,!iarit\ 



- Miniiiiwiia. 



i'i i:in iK.i.i.A rKi:-iMii.i>. n. >//. 



<>-. 

 I nun.: hlk'Iit l.i'l nun.: thi.-kn>".s (i - mm 



i|>ace ovate, moderately convex, with the end- nearly e, ( ual: no dor<al angle 

 In-hind !nit a well marke-l one in fni aj. di-tinct; dor-al edge thick, 



houlf|er like; greatest thickne central; -uface -nmoth. The length vai ie- between 

 l.'i mm. and _'..". mm. 



At tir-t sight ti y much like L.rmuili*. \>\\\ carefullv compared 



they prove unite distinct. The outline i- -oineuhat ditlerent being les- wide (high) 



riorly. the dor-al an^le-are rever-e-1. and thO dor-al e.lges much thicker, while 



the thickness of t e and the ventral n\- hidi mark.- the left 



valve in that -pecie-. wanting. Similar ditlerence- distinguish it from 1.. titini'la. 



hold< about the -aiin- id i- ni>' litlerent in outline. 



Still a- it- vahe- do not overlap ventrally .n;d a- it ha- no dor-al angles and |. 



