AND MESOZOIC FISHES. 
443 
Dej)th of body at a point 115 mm. anterior to base of inferior caudal lobe ; 75 
Length of superior lobe of caudal fin from middle of base of fin ; 85 
Do. from last scales ; 46 
Long side of a scale ; 7 
Short side of a scale ; 5 
Length of head from muzzle ; 90 
Length of head to end of maxillary bone ; 48 
Length of head to free border of preoperculum; 74 
Depth of operculum ; 4(> 
Interorbital width ; 24 
Parietal width ; 39 
Depth of skull from posterior border of [)arietal to interoperculum inclusive; 78 
Depth do. at middle of orbit to dentary bone inclusive ; 53 
This species and genus are of considerable interest as representing lor the first 
time in our knowledge, the Jurassic family of the Lepidotidm on the North Amer- 
ican continent. The generic type is a modification of the typical form, appropriately 
to the fact that the horizon from which it was obtained is generally supposed to lie 
at the base of the Cretaceous system, and Comanche series, of Hill. Dr. Hill, 
through whom 1 obtained the specimen, states that it was derived from a calcareous 
stratum which lies betwmen the upper and lower sands of the Trinity series, at 
Glen Rose, Texas. Other vertebrate remains obtained by Dr. Hill at the same lo- 
cality I determined to belong to a small ci’ocodile. Dr. Hill informs me that numer- 
ous mollusca are found at the same hoi’izon, which he has determined to be of 
Neocoinian age. Dr. Lester F. Ward has determined plants from the same, to be of 
Tuscaloosa (Potomac) age, which is nearly^ Neocoinian. I take the present oppor- 
tunity of noting here that several years ago, Mr. Chas. H. Sternberg sent me from 
Kansas several teeth from the Dakota (upper Cretaceous) sandstone, which I suspect 
to belong to Lepidotid fishes. 
PYCNODONTIDJE. 
The marine formations of the Jurassic and Lower Cretaceous systems are the 
horizons in which species of this family abound. As neither of these formations 
is widely distributed in North America, but few species of the family have been 
observed by American paleontologists. The only species thus far described have 
been derived from the upper Cretaceous formation. 1 now describe live s]tecies 
which ivere found in beds of lower Cretaceous age in Texas and Oklahoma. 
MESODOX ^Vaguer. 
MesODON DIASTEMATTCrS sp. nOV. 
Founded on a vomer of an individual of large size, which supports a consider- 
able number of the teeth in place. There are five series of teetli, of which those of 
58 .lOURN. A. N. S. PHILA., VOL. IX. 
