citAGix.] DESCRIPTIONS OF SPECIES. 103 
the coil (a large part of whose periphery is preserved) must have 
considerably exceeded a foot. The specific identification is tentative, 
as it is based on the comparison of imperfect specimens with Castillo 
and Aguilera's description and figures. The specimen figured is a 
young individual and the only one in the collection that shows more 
than a fragment of a complete volution. 
Genus OLCOSTEPHANUS Neumayr. 
Olcostephanus malonianis sp. n. 
PI. XXIV, figs. 1, 2. 
Shell large and moderately involute, consisting of massive whorls 
which are at least as high as or a little higher than wide, with flat- 
tish-convex flanks and broadly rounded periphery, about one-fourth 
of the height of each inner whorl embraced within the whorl next 
outer; umbilical costae not at all resembling compressed tubercles, 
but heavy, long, and truly rib-like, traversing the lower and middle 
parts of the flank from the lower border to between half and two- 
thirds the height of the whorl, giving place at their upper ends to 
numerous compressed, narrowly round-topped costellae which are 
fascicled mostly in threes at their origin, but are uniformly dis- 
tributed upon the periphery of the whorls, over which they pass 
without interruption, swinging very little forward; suture strongly 
dissected, the two lateral lobes and saddles large and complexly 
branching, the external one especially so. The body chamber is 
unknown. 
Measurements. — The largest known whorl section (which is in- the 
septate portion of the shell) has the height and breadth about 110 and 
105 mm.; an inner one about 58 and 57 mm., respectively. 
Occurrence. — Only a few parts of whorls, most if not all of which 
belong to one specimen, were collected at the locality 1-J miles east of 
Ma lone station. 
The species is intermediate in general proportions between the two 
species of Olcostephanus known from the Alamitos beds — which 
seem to correspond in some measure with the Malone formation— in 
Mexico: O. " af. portlanclicus de Loriol " and O. potosina of Castillo 
and Aguilera. 
Genus PERISPHINCTES Waagen. 
Perisphinctes clarki sp. n. 
PI. XXIX, figs. 1, 2. 
Shell large, discoidal, many whorled, broadly umbilicated; involu- 
tion more than one-half; whorls ovate, the outer ones elevated or nar- 
row-ovate in cross section, narrowed toward the venter, which is 
