LOGAN : FREEZE-OUT HILLS OF WYOMING. 127 



Aviriila Inahi. n. sp. Plate XXVIII, fig. 10. 



Shell convex, medium in size, arcuate-oblong in general outline, 

 greatest convexity in the anterior region. The hinge line is short and 

 straight. The beaks are small, somewhat pointed and turned toward 

 the dorsal border, so that the line of greatest arch of the shell is a 

 sigmodial curve. The anterio-dorsal border of the shell is extended 

 into a moderately large wing, which has its margin rounded and curves 

 slightly toward the beak anteriorly; the posterior border a some- 

 what abrupt curve. The ventral and dorsal borders are convex, the 

 ventral border having the greatest convexity. The surface of the 

 shell is ornamented by obscure radiating lines and more pronounced 

 concentric lines of growth. 



Dimensions: Length, BO mm.: width, 12 mm.; height, 6 mm. 



Geological horizon : No. 13 of the section furnished a few speci- 

 mens of this form. The species occurs with Belemnites densus, 

 Pinna Ituigi, Pleuromya auhcomirt'esi^a, Tancrcdki magna, etc. 



Locality : The Freeze-out Hills, Wyoming. 



Remarks : This specimen, the type, was collected by Dr. J. "SV. 

 Beede, in whose honor it has been named. It is not a common form 

 in the Jurassic fauna of this locality. 



Astarte iHtehtivdi White. Plate XXVII, figs. 13, U. 



Shell medium in size, convex, subcircular in general outline. The 

 beaks are small, subcentrally placed, and prominent. The anterior 

 margin is short and slightly convex. The i^osterior margin forms a 

 broad subelliptical curve. The hinge line is short and ornamented 

 with two transverse cardinal teeth, the anterior of which is the larger. 

 The lateral teeth are not present. The surface of the shell is marked 

 by numerous regular concentric undulations, the intermediate spaces 

 being occupied by minute concentric stria?. The casts of the shell 

 exhibit at the margin a row of depressions which correspond to min- 

 ute projections on the shell border. Test of the shell moderately 

 thick. 



Dimensions: Length, 20 mm.; width, 17 mm.; height, 8 mm. 



Geological horizon : This species is very abundant in the arena- 

 ceous nodules of No. 13 of the section, where it is associated with 

 Pinna kingi, Pleuromya conipressa, Gonionrya montanaensis, Belem- 

 nites densus, etc. 



Locality : Freeze-out Hills, Wyoming ; also from Lake Como, Wy- 

 oming, from which place it was first described by White. 



Remarks : Next to Belemnites densus this species is the most 

 abundant species in stratum No, 13. The shells are in a good state 

 of preservation, as they have been crystallized for the most part int(j 



