OM eT UER HS igs AEP og oY Swe ANS ah ae 
Be A tila tayh es Sa 
| 
ENTOMOSTRACA OF MINNESOTA. 297 
margin broad, rounded at the angles, and expanded into a flattened 
lamina or flange. Ventral margin straight for about two-thirds of its 
length, then bending npwards at an obtuse angle. Dorsal margin 
arched, almost angular in the middle, whence it slopes steeply to the 
anterior border and with a bold curve towards the posterior extremity, 
joining the ventral margin at an acute angle. Seen from above, the 
carapace is ovate, pointed in front, and rounded behind; the greatest 
breadth in the middle. The ventral surface is bounded by two con- 
Spicuous, elevated, arcuate ridges, one at each valve, which together 
enclose a flattened lozenge-shaped area. Parallel to the contact 
margin of each valve runs another straight but much less conspicuous 
ridge, which towards the front curves outward, and joins the external 
ridge at an acute angle, the union of the two forming a slight eleva- 
tion, from which a single ridge runs forward, gradually merging in 
the flattened encircling flange of the anterior border. Seen from the 
front, the shell is sub-triangular, the sides convex, but flattened, the 
dorsum forming a flattened arch; the ventral border perfectly flat, 
and bounded by the projections of the outermost ventral ridges; the 
inner ridges form also conspicuous projections, which run obliquely 
upwards and inwards towards the flattened anterior flange. Lucid 
spots, about six, oblong and irregularly placed, their long diameters 
pointing transversely across the valve. Surface of the shell smooth 
and shining, marked by fine impressed lines forming a pattern simi- 
lar to the imbrications of fish-scales. Color pale greenish or white, 
transparent, with large and irregularly spread patckes of deep olive- 
green or black. 
‘* FEMALE.—Sub-quadrangular. Anterior border flattened, flanged, 
forming with the ventral margin a well-marked angle; rounded above. 
Dorsal margin boldly arched, highest at the posterior third, whence 
it Sweeps round with a deep curve to the postero-ventral angle. 
Ventral margin straight, slightly rising behind, and terminating in a 
flattened squamous plate, which projects backwards, with the appear- 
ance of aspine. The other aspects are similar to those of the male 
shell, except that the ventral surface of the left valve has at the pos- 
terior extremity of its contact margin a flattened squamous plate, 
which is received into a corresponding depression of the opposite 
valve.’’ 
Professor Brady (18) states that the branchial plate of the mandib- 
ular palp arises from the lower side of the palp, thus differing con. 
‘siderably from other Cypridide, Professor Vavra (221), however, says 
that the branchial plate arises from the upper side of the mandibular 
palp. 
‘The first foot in both sexes terminates in three curved claws, the 
central one being the strongest and longest. * * * * * * * 
