FOSSIL CEPHALOPODA. 427 
acanthicum in Sicily, but its whorls are less inflated and it has a 
slightly smaller umbilicus. 
It bears some resemblance to Pertsphinctes Beyricht, Futterer,’ 
which according to its author was the principal form of Perzsphinc- 
tes occurring in the collection of Cephalopoda which he examined 
from Mombasa. That species, however, has more inflated whorls; 
it was regarded by Futterer as closely related to Indian species 
from the Katrol group. 
The Somali species has finer ornaments (which are not inter- 
rupted on the peripheral area), and is a much more involute shell 
than Per. bathyplocus, \Waagen” from the middle portion of the 
Katrol group (= Upper Oxfordian to Kimeridgian); whilst its 
ornaments are coarser, the primary ribs more regularly bifid, and 
its involution greater than in Per. alterneplicatus, Waagen,’ a species 
also from the Katrol Group in the Kachh Jura. 
2. Perisphinctes cf. frequens, OPPEL, sp.4 
This species is represented by a number of fragments, the largest 
and best preserved of which is part of a whorl about 170 mm. in 
diameter. But this whorl bears indications of a succeeding whorl, 
so that the specimen must have attained aiarge size. Rather more 
than one-fourth of a whorl is preserved, with a portion of the pre- 
ceding whorl attached. There are about fifteen primary ribs in a 
quarter of a whorl, and each of these at about from one-third to 
one-half of the width of the lateral area from the periphery divides 
into three ribs which pass uninterruptedly and ina straight line 
over the peripheral area. The transverse section of the outer 
whorl (that is preserved) is oval or subquadrate, the sides being a 
little flattened and convergent, and the greatest width being at 
about one-third of the height of the whorl above the inner edge of 
the whorl. The preceding whorl is more oval in section and 
agrees better with Oppel’s and Waagen’s figures of Per. frequens. 
At the anterior extremity of the specimen the dimensions of the 
outer whorl are: height, 53 mm.; ditto above preceding whorl, 
1 Zeitschr. deutsch. geol. Gesell., vol. xlvi. (1894), p. 9, Pl. IL, figs. 1, 1a; 
Deane Dis" 3s 
2 Pal. Indica, ser. ix., Jurassic Fauna of Kachh, vol. i., p. 192, Pl. L., figs. 
Tac Dwelov75 
8 Pal. Indica, ser. ix., Jurassic Fauna of Kachh, vol. i., p. 199, Pl. L., figs. 
2a, by 1675. 
4 Pal. Mittheil., vol. ii., p. 295, Pl. LXXXVII., figs. 1a-c., 1865. 
