106 MALONE JURASSTC FORMATION OF TEXAS. [bull. 26G 
P. contiguus Catullo, and that seems to agree sufficiently with tlw 
description and illustrations of P. potosma C. and A. The lateral ribs 
in form, size, interspacing, and manner of trifurcation, are those oi 
P. contiguus, from which the Malone shell differs in the more ante- 
riorly inclined lateral ribs and in having the ventral ribs distinct!} 
curved forward as they approach the periphery, on which they arc 
slightly extinguished. The last-named feature, however, is not a 
specific difference; for while the ventral ribs in P. contiguus an 
usually uninterrupted, a slight peripheral attenuation of them n 
noted by Toucas" as occurring in some varieties of this species in tht 
Carpathians. 
The fragment agrees in size with an intermediate part of the outei 
whorl of P. contiguus or P. potosinus, and the cross section of whorl I 
which it indicates is about three-fourths as broad as high, measuring' 
-2\ mm. in height and L8 or L9 mm. in breadth. 
Siemiradzki b refers to P. potosinus as apparently identical with 
P. hoheni Behrendsen, c but there seem to me to be considerable dif- 
ferences between the two species. These differences, if we accept tin 
description and the figure of the adult (PI. XVII, fig. 1) and exclude 
(he -mailer and doubtfully pertinent figure (PI. XXTV, fig - . k J) given 
by Castillo and Aguilera of their Perisphinctes potosinus, are as« 
follows : 
/'. kokeni. /'. potosinus. 
Involution I,. Involution § to |. 
Whorls broader (thicker) than high. Whorls higher than broad. 
Whorl cross section quadri laterally Whorl cross section Hat-sided ovate. 
rounded. Venter rounded. 
Venter flatly rounded. Lateral ribs bifurcate, the larger nuni- 
Lateral ribs bifurcate. ber becoming trifurcate on the last 
Simple part of lateral ribs rather whorl. 
slender. Simple part of lateral ribs rather stout. 
Perisphinctes felixi C. and A. 
pi. xxi it, eg. 2. 
Perisphinctes felixi Castillo and Aguilera, is«.>r>, Bol. ('(an. Geol. Mex., No. 
1. p. 'jr., I'l. XVI, fig. 1. 
A species of Perisphinctes apparently not distinct from P. feliax 
C and A., but intermediate in some of its characters between the latter 
and the closely allied, if indeed really distinct P. lauri C. and A., 
is represented from the locality 1J miles east of Malone station by a 
specimen showing part of three successive whorls. 
The whorls are rounded in cross section, having their height and 
"Bull. Soc. Geol. France, 3d s£ei\, Vol. XVIII, p. 582. 
b Monogi\ Beschr. Perisphinctes, p. 17<>. 
c Zeitschr. d. Deutsch. Geol. Gesellsch., Bd. 4:;, p. 400, pi. 24, figs. 1 and 2. 1891. 
