302 ARCHEGOCOPTIS. 



nearly straight transverse rows. Teeth of normal Helicid 

 type, the basal-plates square, about as wide as long, or wider. 

 Central teeth as large as the adjacent laterals, tricuspid, the 

 mesocone large, with conic cusp slightly longer than the basal- 

 plate; ectocones minute. Laterals similar but asymmetrical, 

 with no trace of an entocone on any of the teeth. The mar- 

 ginal teeth are merely shortened laterals, with rounded, 

 simple mesocones, and small, simply conic ectocones, the 

 cusps obsolete on the outermost teeth as usual (pi. 63, figs. 48, 

 49, 50, A. crenata). Soft anatomy otherwise unknown. 



Distribution, western Haiti. Type Cylindrella crenata W. 

 & M. (Archegocoptis, first of the cut-off race). 



The striate, not plaited jaw, and the normal, Helicid radula 

 isolate Archegocoptis among Antillean genera of Urocoptidce, 

 and ally it to the continental genera Eucalodium, Anisospira, 

 and their kin. By the structure of its slender axis, and of the 

 steeply-sloping plug at the summit Archegocoptis stands 

 nearest Eucalodium; but in the latter genus there is usually a 

 minute axial perforation, while Archegocoptis has an imper- 

 f orate axis. The exact affinities of Archegocoptis to the vari- 

 ous other genera of Eucalodiina will be determined by the 

 structure of the free retractor muscles and other soft parts, 

 which cannot be worked out from the dry specimens in my 

 possession, which were collected by Mr. J. B. Henderson, Jr., 

 at Jeremie, Haiti. AA 7 hether the genus is to be regarded as a 

 remnant of the original stock of Antillean Urocoptidcu, retain- 

 ing the archaic type of mouth parts, or is a later immigrant 

 from the continent, it is at present impossible to decide. 



Key to species of Archegocoptis. 



1. Basal keel very strongly projecting; peristome hardly 

 expanded. A. eximia. 



2. Basal keel a moderately strong cord ; peristome expanded 

 and somewhat reflexed. A. crenata. 



1. A. EXIMIA (Pfeiffer). PI. 38, figs. 1-4; pi. 41, figs. 67, 68, 



69, 70. 



Shell cylindric below, the upper half or two-thirds slowly 

 tapering to a rather wide truncation, closed by a steeply slop- 



