252 PALEOZOIC PALEONTOLOGY. 
DALMANITES ASPINOSA Nl. Sp. 
Plate XGXols Birds: 
Description.—Known only from the pygidium, which is longitudi- 
nally semi-elliptical in outline, obtusely pointed posteriorly. Axis 
regularly tapering and rounded posteriorly; in the type specimen 
reaching to within 4.5 mm. of the posterior margin, which makes it 
about sixth-sevenths of the entire length of the pygidium; marked by 
about sixteen annulations, which gradually decrease in size posteriorly, 
until they become entirely obsolete. The plure are rather strongly 
convex to the margin, with no flattened or concave border; marked 
by ten prominent, narrow, grooved ribs, which extend to the margin 
of the pygidium and are separated by broad, concave furrows. 
The dimensions of the type specimen are: length, 32 mm.; width, 
40 mm.; convexity, 9 mm. 
Remarks.—The only specimen of this species in the collection which 
is in any degree complete is an internal cast of the pygidium. This 
specimen, however, preserves essentially all the characters of the 
pygidium, though another specimen, not a cast, would show the 
pleural ribs to be somewhat broader. The species differs somewhat 
conspicuously from any of the other Silurian members of the genus 
in the American faunas, and may be recognized by the absence of any 
spinous extension from the posterior extremity, by the absence of 
any flattened or concave marginal border and by the sharp pleural 
ribs, which extend to the border of the pygidium. 
OSTRACODA. 
LEPERDITIA ALTOIDES Nl. sp. 
Plate XXIII., Figs. 1-2: 
Description.—Carapace of medium size, obliquely subreniform, nar- 
rower in front, somewhat variable in proportions; valves strongly 
convex, gibbous in the middle. Dorsal margin straight, from three- 
fifths to two-thirds the total length; dorsal extremities obtusely an- 
gular, posterior margin broadly rounded, ventral margin convex, 
