234 PROCEEDINGS OF THE ACADEMY OF [Mch., 



This form has hitherto been referred to A. chiricahuana , from which 

 it differs chiefly in the greater inflation of the latter part of the last whorl. 

 This is noticeable in a side view, and is seen prominently above the 

 aperture in a front view. It differs from A. pseudodonta capitanensis 

 chiefly by wanting basal teeth. 



In such simplified forms as this, it is not easy to determine the true 

 relationships by the shell alone. When the genitalia can be examined 

 the affinities of A. ashmuni and A. a. robusta. wnll doubtless become 

 clear. There is an albino in Mr. Ashmun's collection. 



Group of A. thomsoniana. 



Aperture of the shell with parietal, outer and basal teeth, the latter 

 often bifid, divided into two contiguous tubercles. Length of the sper- 

 matheca and its duct 60 to 65 per cent, that of the penis, epiphallus 

 and flagellum in known forms. 



These forms are from northern central New Mexico. They have been 

 investigated chiefly by Prof. T. D. A. Cockerell and his pupils. 



By their genitalia and shells they are related to the southeastern 

 Arizona group. Three forms are perhaps sufficiently differentiated to 

 require names: A. t. porterce, A. thomsoniana and A. t. pecosensis. 



Ashmunella thomsoniana (Ancey). PI. XIII, figs. 27-30. 



Helix lerettei Bland var. thomsoniana, and var. orobtena Ancey, Concholo- 



gist's Exchange, II, p. 64 (November, 1887). 

 Ashmunella thomsoniana (Anc.) Pils. and CklL, Proc. Acad. Nat. Sci. Phila., 



1899, p. 192; Ancey, Jour, of Malac, VIII, p. 75, 1901; Pilsbry, Proc. 



Acad. Nat. Sci. Phila., 1900, p 108, fig. 2 (genitalia of specimen from Santa 



Fe canyon) ; Ckll. and Cooper, Nautilus, XV, p. 109, February, 1902, 



with mut. alba C. and C, /. c, p. 110 (Canyon Diablo) ; Ckll., Nautilus, XVI, 



January, 1903, p. 105 (Pecos Pueblo). 

 Ashmunella thomsoniana coopene Cockerell, Nautilus, XV, p. 35, July, 1901. 

 A. t. antiqua Ckll. and Coop., Science, December 27, 1901, p. 1,009; Nautilus, 



XV, p. 110 (Pleistocene, Las Vegas). 



Specimens from J. H. Thomson, part of the original lot from Santa 

 Fe Canyon, are before me, and two are illustrated (PI. XIII, figs 

 27,28). 



It is narrowly umbilicate, brown and glossy, finely striate, wdth very 

 faint traces of incised spirals on the last whorl. There are 5 whorls. 

 The characters of the aperture are sufficiently shown by the figures, the 

 only ones published to this time. The basal tooth is simple in all 

 specimens I have seen from the type canyon. 



Alt. 6.9, diam. 13 mm.; whorls 5. 

 " 6.9, " 12.2 " " 5i. 



" 6.9, " 13.1 " " 5i 



The specimen I dissected in 1900, collected by Prof. Cockerell at 



