. \ I'. I 1 ' 



i mimurrn- 



I'KIMI i IKI.I v in i.v 



n. ill, minparatm-ly -Imrt form. witli -ulic.|iial. rounded cud-. broadly 001 

 ventral margin aii<l a -trai^ht dark, tin- extremities (if \\hicli howe\er art- -carcely 

 angular: mc.-ial dcpre--ion \er\ -hallow but wide, taking up a large port ion of tln> 

 ri'iitni-iliir-al region; edges simple, or with un obscurely defined. narrow border. 

 Though reMMiihling se\> of I'riinitin. fmin which it i- distinguished l.y the 



wiiltli ami -hallowne-s of the me-ial dcprc ion. I cannot lind any de-cril>ed OStracode 

 with which it is strictly identical. 



.niiiiii'iii in th>- IIIWIT |>.rt of tlii- Trcntiiii -li.ili-- ii'-;ir I oinilalo, 



I'KIMITIKI.I.V 01 I'lrirli. 



IM.\TI CUB i M 



lit I 'i.un n. l'7 ii, p. in. pi. vii, UK'. 4. 



n. I s *!'. C'liilri. ' 50. 



;rl. Jniir ' 



rfhtO.59 nun : ihirknr^ o 4 nun. 



.ipace convex, scarcely oblitjue. oKloni.'. with a long, straight hinge, ami 

 rather wpll-inurkeil 'lor-al angles; ventral margin gently arcuate, nearly parallel 

 with the hack, the anterior In^ht of the valves being but little less than the poste- 



rior: po-tfi-ior !ii.n_'iii i iii'lr 1 from the dorsal angle: anterior margin obliijurly 



triiiicateil in the upper half, sharply nuiile<l at the middle; a narrow but well- 

 letint-1 border be^in- at thi> joint and follows the outline to the post-dorsal angle; 



tin- jio-terior extremity of each valve, ii-nally -n: l>eneath the miil-liight, 



a -tron^r -pine projects outwardly or p.^t.-riorly: in a dor-al or ventral protilc- the 

 end.- are blunt and the side- of i.\\< straight or just appre.-ialily concave: in 



front of the mi-Idle of the dor-al .-lope there is a wide and ver\ faint depression, and 

 in the lower jiart of tlii- a invariably distinguishable. Speci- 



mens are usually about 1.0 nun. in length. A small variety occur- at Cincinnati. 

 <hio. avera^'in^ between 0."> and i.r, mm. in length. 



All the American -pecimen- of ti .-xceptin^ I lie val\. I \>y me 



from M.iuitolia i >i}i. rif.) are remarkably con-taut in all their c ha racters. Indeed, out 

 of over tifty free caraj)aces and valve-. I was unable to find one that ditl'ered enough 

 from tis_ r . ~tl to make it worth the while to prejiare drawing- of it. I 1 . :hi- 



con-tancy in mind it is ratlier surjiri-in^ to learu that ProfLJones fooad Considerable 

 varialiility among the Brit; MICH- n-fcrred by him to the- 



