NOTES ON SPECIES 487 



species, greater in others, from corresponding species in the Kaibab 

 below. In the former cases the difference is not usually sufficiently great 

 to receive even verietal distinction, in the latter specimens it frequently 

 reaches a specific differentiation. This change is apparently mostly due 

 to the passage of time, not entirely to a different environment. Just as 

 the upper Kaibab limestone, more or less arenaceous, followed the middle 

 Kaibab gypsiferous red beds, so the fossil-bearing arenaceous limestone 

 lenses in the Moenkopi are separated by gypsum-bearing red beds. In 

 each case the fauna lived in shallow, near-shore seas, which were probably 

 only slightly more open in the case of the Kaibab than in that of the 

 Moenkopi. 



With the knowledge that Doctor Girty is working on this fauna, it was 

 decided that the description of new species should be based on the larger 

 and geographically more extended collections in the N'ational Museum. 



Notes on a few of the species are here appended. 



Pentacrinus sp. — This is a new species. It is very small, a rather large 

 joint measuring 3 millimeters in diameter. The depressions of the 

 sides are shallow, a joint varying from a distinctly star-shaped form to 

 almost a five-sided polygon. The elliptical figures upon the face of a 

 joint are broad, filling up the intermediate space with their radii, though 

 inside each ellipse the smooth space is narrow. Axial opening is minute, 

 round. 



Cf. Orhiculoidea nitida (Phillips). — Our single specimen agrees closely 

 with Walcotf s specimen from the Eureka District, Nevada, as figured by 

 him in the U. S. Geological Survey Monograph 8. It has a diameter of 

 20 millimeters, a height of 4 millimeters, with coarse concentric striae. 



Ortlwtetes rrassus (M. & H.). — All of the specimens identical with 

 this common species are fragmentary. Some of them appear to approach 

 rather closely Girty's Guadalupian Derhya ? creniilata, while one from 

 the Kaibab Plateau may be his Derhya nasuta. 



Chonetes geinUziamis Waagen. — The specimens identified with this 

 species exhibit, when exfoliated, strong radiating markings due to the 

 structure of the shell ; where not exfoliated the surface shows numerous 

 minute spine bases. 



Puf/nax osagensis Swallow. — Our specimens are similar to those de- 

 scribed and figured by Girty from the Guadalupian of Texas.* The fold 

 and sinus are of moderate strength, with three rounded plications upon 

 the fold and three upon each side, the last lateral plication being faint. 

 Our specimens may be slightly broader in proportion to height than tlie 

 Guadalupian ones. 



" U. S. Geol. Survey, Prof. Paper 58, 1908. p. 317, pi. 24, fig. 16. 

 XXXIV— Bull. Oeol. Soc. Am., Vor,. .30, 1918 



