,.i,\ 



Krux.|l>.| 



.ily r.KKMIKRKLUI'.l 

 M MI \l SKI.l.A. n. gen. 



Carapace small (I . nun. in length), somewhat elongate, suhelliptical. 



obscurely triangular ur semiovate in outline, the dorsal margin more coiuev than 

 the ventral, the latter straight or but gently convex; with moderately thick and 

 very une.|iial valves; rL'ht \alve the -mailer, drawn out posteriorly into a strong 

 -pine-like process; left valve overlapping the right all around. 



Type: AV-/ /*// / iw/(yii///i.v, n. -p. 



At ; 1 am ar,|iiainted with only four that should le placed in 



thi- genii-, vi/.: the two about to be described, Hnin/in mificostiensis Jones (Quart. 

 .lour, tieol - . \lvi, p. ~>lx Is'.M)) from the Hudson Hiver or Cincinnati forma- 



tion of the island of Antieosti, and an unde.scrihed form (near A', .in-milii) which is 

 rarely met with in the upper beds of the same formation in Ohio and Indiana. These 

 !o not agree with /./////// since the spine-like process is not formed by the 

 tapering end- of h,,tl, valves. Imt i- restricted to the right valve, the left valve being 

 rounded po-teriorly and resembling the corresponding valve of a thick-shelled 

 HyHixri/iiri*. We have t here fore t he ditlerence that while the two valves of a Bainl'm 

 are similar in outline, they are quite different posteriorly in A"/ </// //<;. 



The spine-like process reminds of some of the species placed by the author under 



genus Beechtrella.* If there is any true relationship between AV</r/7A/ and 

 Beechertll, and I confess that I am strongly inclined to believe there is. then the 

 Btecherella* were probably all described and figured in a reversed position. Another 

 thing that has become more evident than formerly is that more than one generic 

 has been included under Hfx-hrnlln. Considering the strongly marked peculi- 

 aritie- of the type species, B. niriwit<i. it seems probable that we shall eventually 

 find it desirable to restrict the genus to it 



of />'. snlitumiil'i we know only the right valve, and this is exceedingly like the 

 same valve of Kr>m*ell<i ammt'i. Still. 1 hesitate to say that it should be referred to 

 the present genus >mce it may be shown that it, like /.' / /-/.////. has the posterior 

 -pine on the overlapping instead of the smaller valve. In the last species namely, 

 the right valve seems to overlap the left, though the overlap is very -light and 

 scarcely di-tingui-hable. Should the relations of the valves (with respect to 

 overlap) in these two species prove to be really the reverse of what we know to 

 be the case in Knium-Un. a di-tii: :i<- grouping for them would probably \- 



justifiable. 



\!ii<-rton G. Till. pp. W7-JO4, pi. t. October. ll 1.. a ;.;;,. i.e new eou BMrfer- 



tUa. with ls ow >Doctn and ooe variety, all derlred fnmi the Ifrmvt HcWt-rlirrx -i ria . ' ' 



