PLATE V. 



Dielasma schucherti. Page 148. 



1.— Interior of the shell of a young specimen, 5 mm. in length, showing 

 loop, foramen, etc. The loop should be more angular where it begins its 

 curve. No. 59 of collection from Dozier, Tex. 



la, Ig, Ih, li, Ij. —Young specimens, showing some of the variations in 

 form, the muscular impressions (elevations in casts) in the shell which later 

 fill to form a sort of platform. Most of the figures are a trifle over natural 

 size ; Ih shows the beginning of the plications. Sometimes the shells at- 

 tain a much larger size before showing the plications as in 11. Specimens 

 Nos. 32, 30, 29, 28, 31, respectively, from Whitehorse spring, Oklahoma. 



16. —Adult specimen, brachial aspect, showing bipHcation, crural and 

 lemellar impressions. 



Ic— Side view of same; Id is the pedicle view, showing impression of 

 dental lamellae. No. 25, Whitehorse collection. 



le,— Another specimen from Dozier, younger than 1, showing loop still 

 disconnected. There is a more acute angle, than shown in the drawing, 

 where the loop first rolls outward from the supports. No. 125, Dozier col- 

 lection. 



1/.— An abnormal specimen of pedicle valve showing a tendency to de- 

 velop more plications and strong sets of dental lamellae. No. 24, White- 

 horse collection. 



lA;.— Lateral view of robust specimen, still immature. 



IZ.— A figure of a half-grown individual. No. 27, Whitehorse collection. 



Im.— A portion of a replaced shell in a mold, showing the punctse. Very 

 highly magnified. Under an ordinary lens they appear as the ordinary 

 meshwork of Dielasma. No. 23, Whitehorse collection. 



Aviculopecten vanvleeti. Page 159. 



2.— A very large, poorly preserved specimen. Natural size. No. 13 

 Whitehorse collection. 



2a. —A somewhat smaller specimen, showing the nature of the surface 

 marks and one of the ears. The drawings of this species are poor and ex- 

 press very inadequately the surface characters of the species. They are 

 like those of A. occidentalis, but with three to five large ribs, more pro- 

 nounced than in that species. No. 10, Whitehorse collection. 



26. — Broken opposite valve of another specimen probably of this species. 

 It is remarkable in being almost free from surface marks. No. 17, White- 

 horse collection. 



2o. — A slightly flattened valve of this species showing the opposite ear 

 from that shown in 2a. The figure shows the ear a little too convex and the 

 sinus below it too shallow, changing considerably the expression of the shell. 

 No. 11, Whitehorse collection. 



(over) 



