74 FAUNA 01' BALUCHISTAN. 



therefore obliged to suppose that the form described as Indoceras baluchUtanensia 

 really represents a new genus, which is characterised by a bipartite external saddle, 

 divided by a deep and broad adventitious lobe, and numerous auxiliary lobes. 



I fully realize the inadvisability of establishing a new genus on characters 

 which have been deduced from a single species only, and are not confirmed by 

 being common to a number of species ; but following the development of the sutural 

 line of Indoceras bftluchistanensis, I cannot admit that the largest lobe should not 

 be homologous to the first lateral of other Ammonites, but should represent a second 

 adventitious lobe. The diagnosis of the genus Indoceras would, therefore, be as 

 follows : 



Shell discoid, consisting of rather high whorls, enveloping each other so fully 

 that only a very narrow umbilicus remains. Sides flat, in the earlier stage 

 provided with indistinct radial ribs, which become effaced in later age. Sipho- 

 nal side sharp in young specimens, flattened, with an indistinct median keel, ac- 

 companied by an obtuse rounded keel on either side, in adult specimens. Siphonal 

 lobe broad and short ; first lateral broad and short, denticulated ; second lateral lobe 

 much shorter and narrower than the first one ; about six very short ' and narrow 

 auxiliary lobes, of which only the first two are denticulated. External saddle 

 rounded, rather broad, divided by an auxiliary lobe of considerable depth into two 

 branches ; other saddles rounded, short, but much broader than the lobes. 



Indocekas baluchistanbnsis, spec.'nov. PI. XXI. fig. 2-2a, PI. XXII. fig. 1-lb, 



2-2b, 3-3a, PL XXIII, fig. 1, 2-2a. 



I. II. III. IV. 



Diameter of the shell 60 mm. 65 mm. 80 mm. 103 mm. 



Diameter of the umbilicus .... 4 „ ? „ 4 „ 4 „ 



Height of the last whorl from the umbilical suture 33 „ 35 ,, 44 „ 58 „ 



H eight of the last whorl from the preceding whorl 20tP) „ 21 ,. ? j. 31 „ 



Thickness of the last whorl . . . . 15 / 19 „ 21 „ 25 „ 



Approximate number of septa to one volution . 26-28 „ ? „ 28-30 „ ? „ 



The shell is apparently of moderate size and discoid ; the diameter of the largest 

 specimen, which must be a full grown one, to judge from the closely following 

 septa at the end of the body chamber does not exceed 125 mm. in diameter.^ It 

 consists of rather high laterally compressed flat whorls, which overlap each other 

 so completely that only a very narrow umbilicus remains, which was probably nearly 

 filled by a shelly callosity. 



The smallest well preserved specimen, which apparently retains the body 

 chamber to its full length, exhibits some interesting features regarding the charac- 

 ter of the siphonal side and the changes which this undergoes during the growth 

 of the shell. At the time when the shell barely exceeded 40 mm. in diameter, the 

 sides were very flat, but showed a line of very indistinct radially elongated 

 nodules, close to the siphonal edge, apparently the last remains of very flat and 

 broad radiating ribs, which became somewhat thickened towards the upper end. 



> The specimen is not fully preserved, but to judge from the lower part of the end of the body chambei, 

 it must have been approximately of this. size. 



