ARCHEGOCOPTIS. 301 



nuclear and about a dozen subsequent whorls ; those following 

 the nucleus are rather strongly obliquely ribbed with close set 

 fine riblets which become fainter over the main body of the 

 spire and reappear again on the last whorl; aperture entire, 

 simple, rounded, but a little angular at the posterior outer 

 corner; the umbilicus closed, the spire gradually enlarging to 

 the eleventh whorl, then slightly attenuated. Alt. 12.5, max. 

 diam. .32 mm." (Dall). 



New Mexico: In the debris of the Rio Grande at Mesilla 

 (T. D. A. Cockerell). 



Holospira (Haplostemma) cockerelli DALL, Nautilus, xi, 

 p. 62 (Oct., 1897). 



' This is the second species of Haplostemma, and one of the 

 smallest, if not the smallest, Holospira yet recorded." 



HOLOSPIRA ROEMERI (p. 97), var. minor STERKI, Nautilus, 

 vi, p. 6 (nude name). COCKERELL, Nautilus, xi, p. 136 (last 

 four lines), based upon var. b BINNEY, Man. Amer. Land 

 Shells, p. 422 (" Smaller, more ventricose above; whorls 12, 

 the last more briefly loosened; length 11, diam. above the 

 middle 4 mm."). This form is merely an individual vari- 

 ation. 



Genus ARCHEGOCOPTIS Pilsbry, 1903. 



Shell pillar-shaped, broadly truncate, with a flattened, 

 steeply-sloping plug, and six to ten whorls in adults; the 

 amputated early portion of the spire long and many-whorled, 

 attenuate; protoconch of nearly 4 whorls, the first one high, 

 turned down and smooth at the apex, elsewhere sculptured 

 with irregularly-spaced vertical riblets; following whorls 

 with groups of short riblets below the suture (pi. 41, fig. 69). 

 Surface of the post-nepionic shell lusterless, densely sculp- 

 tured with fine, waved, irregular stride (pi. 41, fig. 70). 

 Whorls flattened, the last carinate below, shortly free in front. 

 Aperture subcircular, the peristome continuous. Axis slen- 

 der and straight, imperforate. 



Jaw arcuate, moderately strong, densely and irregularly 

 striate vertically, 1.2 mm. long (pi. 63, fig. 46 X 60; fig. 47 X 

 300, A. crenata). 



Radula wide, of the usual proportions, with 21.1.21 teeth in 



