1905.] NATURAL SCIENCES OF PHILADELPHIA. 237 



Miss Mary Cooper collected specimens in I\Ianzanares Valley, near 

 Rowe, New Mexico, which have been reported on b}' Prof. Cockerell 

 and Miss Cooper {Nautilus, XV, p. 109). They are in all respects like 

 those of the type locality except that the inner basal denticle is more 

 obsolete, as in fig. 39. The curve of diameters is the same as in the 

 Beulah lot. The specimens I have seen are from 15 to 16 mm. diam. 



A single specimen I have seen from Cooper's Mill, near Rowe, New 

 Mexico, measures 8.7 x 16 mm., with 5| whorls. The inner basal den- 

 ticle is low, as in Manzanarcs shells. 



The shells from Pecos, New Mexico (PI. XIII, figs. 43-45, collected 

 by Cockerell), are intermediate between thomsoniana and poiierce; the 

 size being that of the former, while in 14 out of 17 specimeiLS before 

 me the basal tooth is double, as in porferce. In the others it is simple, 

 as in thomsoniana. The umbilicus is rather wide, as in porterce. Prof. 

 Cockerell refers the form to A. t. coopera;. Its location depends upon 

 whether size is more important than the teeth as an index of 

 affinity; but the question of name is of minor importance in view of 

 the intergradation of the whole series. Specimens measure : 



There is practically no variation in number of whorls, or in the pro- 

 portion of altitude to diameter. The variation in diameter is not great, 

 but serves to connect thomsoniana and porterce, but the skew of the 

 curve is toward the larger size of porterce. 



Ashmunella thomsoniana pecosensis ckll. PI. xill, fig. 88. 

 Cockerell, Nautilus, XVI, p. 105, January, 1903. 



Shell like thomsoniana in shape, size, the small umbilicus and the 

 simple basal tooth; but differing in sculptiu-e, a coarse, low costation 

 being superposed upon minute growth-lines and microscopic spirals 

 similar to those of A. thomsoniana. Aperture as in thomsoniana, the 

 "lip and teeth stronglj^ developed, the basal tooth single." 



Alt. about 6.3, diam. 11.8 mm. 



Valle ranch, Pecos, New Mexico. A Pleistocene fossil. Type No. 

 84,209, A. N. S. P., collected by T. D. A. Cockerell. 



