CEPHALOPODA. 21 



The discoid shell consists of low rounded whorls which increase very slowly 

 in height and scarcely overlap each other. The umbilicus is therefore fairly wide and 

 rather deep. The sides are rounded and drop very suddenly towards the umbilicus 

 and the siphonal side, which is slightly flattened. Cross-section elliptical. 



The sides are covered with very regular strong and sharp ribs, which rise at 

 the umbilical suture, and run with a slight curve towards the aperture, till at 

 about f of the height of the whorl they split iuto two or three thinner branches 

 which run oyer the siphonal side, exhibiting a slight backward curve in the centre, 

 with a few rather deep contractions. 



Sutural line not seen. 



Locality and stratigraphical position. — Mazdr Drik; Polyphemus-livaesione. 



Semarks. — This species is easily distinguished from all the others by its evolute 

 shell consisting of low rounded whorls. Although I have no. specimens attaining 

 the size of those described by Professor Waagen, those I have examined agree so 

 well with his fig. 2 that they must be considered as identical with that species. 



Professor Waagen mentions that the lobes of the specimens from Kutch do 

 not quite agree in every particular with Gemmellaro's drawing : as that author lays 

 special stress on the sutural line of Perisphinctes recuperoi, by which it is distin- 

 guished from Ferisphinctes euryptyohus, Neumayr, it may perhaps be probable that 

 the Kutch specimens represent a form different from Gemmellaro's species. How- 

 ever, whether this view is correct or not, the specimens from Baluchistan certainly 

 represent the same species as those from Kutch. 



Perisphinctes ABBRRA.NS, Waagen. Plate XIII, fig. 5. 



1875. Perisphinctes aberrans, Waagen, Palaeontologia Indica, Jurassic Fauna of Kutch, Vol. I, p. 175, PI. XV, 

 fig. la, h, c, 2a, b. 



Dimensions. 



Diameter of the shell 223 190 mm. 



„ of the umbilicus ......•' 97(r) 70 „ 



Height of the last whorl from the Timbilical suture ... 77 63 „ 



„ „ „ from the preceding whorl ... ? P 



Thickness of the last whorl ? ? 



The shell consists of low whorls, laterally compressed, which very gradually 

 increase in size and by overlapping each other to a little less than half their height 

 produce a wide umbilicus, exposing no less than seven whorls. The umbilical wall 

 is rather high and the umbilicus therefore tolerably deep ; the umbilical edge is 

 rounded and the flat sides slope very gradually towards the rounded siphonal side. 

 The ribs which begin on the umbilical wall are rather strong, considerably inclined 

 forwards, and branch into somewhat thinner ribs which pass round the siphonal 

 side. On the inner whorls the ribs are very well marked, but with increasing size 

 they become flatter and more indistinct, till they entirely disappear on large 

 specimens similar to that figured. So far as could be ascertained, the specimens 

 under examination exhibit no contractions. 



