362 MEXICAN BOUNDARY SHELLS— DALL. 



ramentosa ahbreviata has the apex, surface, and geueral form of B. arte- 

 mesi((, but with a g^yrate pillar and pervious axis in the last whorl. In 

 the only specimen 1 have seen of variety ahbycriata, the axis is not per- 

 vious and the shell is pathologically distorted. I do not doubt that 

 some of Dr. Cooper's examples of this form (of which only nine speci- 

 mens were collected in two years) have a pervious axis, but I am 

 inclined to regard the sliell as a variety of B. artemcsia rather than C. 

 ramentosa, and as a peculiar pathological product rather than a nor- 

 mal development. I fully agree to the proposition that B. ahbreviata, 

 if it is normal, presents characters (analogous to the gyrate axis of 

 Leptobyrsus spirifer in its penultimate whorl) in many respects inter- 

 mediate between B. artemesia and ^'■Columna" ramentosa, and that all 

 three are derived from the same stock. The specimens had nnfortu 

 nately been put into very strong alcohol at first and consequently had 

 been so contracted that not only the head and associated parts, but also 

 the anterior end of the foot had been invaginated within the general 

 surface of the body and all attempts at relaxing them failed entirely. 

 It was observed, however, that the body above was slaty black, with 

 large, elongate, pustular granulation, the foot paler, bordered above and 

 at the edge by a narrow row of shorter pustules distinct from those of 

 the general surface. The sole was marked by a deep median groove, on 

 each side of which, extending to the marginal border, is a broad rep- 

 tary band or longitudinally striate, nearly smooth reptary surface. 

 The tail end is somewhat rounded with no visible mucus gland; the 

 front edge substruncate. The characters of " Columna-' ramentom were 

 similar on a smaller scale. 



The jaw of B. artemesia is fjiirly strong; the upper part smooth, the 

 lower part with about 12 somewhat irregular ribs, smooth or low on 

 the side toward the median line and with a thin, ragged, projecting 

 edge outwardly. They looked as if the jaw had been repeatedly split 

 upward from the cutting edge about half way to the upper margin, 

 with a dull knife held obliquely. These ribs, if they can be so called, 

 hardly project from the surface of the jaw, and contrast very strongly 

 with the few strong distant ribs which are found on the ydw o( Bh odea. 

 The jaw in these Bulimuli is always reinforced by a thin chitinous 

 sheet which protects the roof of the mouth from the points of the 

 teeth on the radula. It is usually left off or neglected in figures of the 

 jaw. This appendage is connected with the lower margin of insertion 

 of the jaw proper and extends back about three or four times as far as 

 the antero posterior width of the jaw. It is usually smooth and almost 

 transparent. In B. artemesia the anterior central part has the i)unc- 

 tate, or rather cellular appearance of adenoid tissue, being covered 

 with minute circular impressions or markings only visible under high 

 magnification. If these are elevations or depressions on the surface 

 of the sheet (which for convenience may be called the oral shield) they 

 are probably on the side which is attached to the flesh and are perhaps 

 due to the cellularity of the tissue they protect. (See Plate I, fig. G.) 



