302 
INFERIOR 
OOLITE 
AMMONITES. 
Haplopleuroceeas mundum, S. Buchnan. Plate LI, figs. 11, 12. 
A somewhat degraded development of Haplopletiroceras suhspinatum, to the 
type form of which it is more or less connected by the specimen depicted in 
PI. LI, figs. 8, 9, though this specimen has practically obsolete ventral furrows, 
pointing to divergence in another direction also. Haplopleuroceras mundum is 
separated from the typical H. subspinatum by broader and more compressed 
whorls, finer and more closely-set ribs, and smaller spines. The more distant 
ribs of the inner whorls are the remains of the " suhsjjinatum'^ stage ; while the 
compressed, more quickly-coiled outer whorls, with their less vigorous ornamen- 
tation, point to decadence in the normal manner. 
This form occurs with H. subspinatum, but is decidedly rare. 
Figs. 11, 12 of PI. LI furnish a very good idea of this " species." 
SoNNiNiN^ {continued). 
Genus — Doesetensia,^ S. Buckman. 
(T(/^e — DoESETENSiA Edoitaediana, d'Orbigny sp.) 
— Harpoceeas (pars) auctorum. 
1885. Gi-EUPPE DES Haep. coeeuoatum, Haug (pars). Beitrage Monogr. Sarpo- 
ceras ; Neues Jalirbuch fiir Mineralogie^ 
Bl.-Bd. iii, p. 674. 
Discoidal, compressed, carinate and sulcate, or acutely carinate, or hollow- 
carinate. Whorls ornamented with subdirect, ventrally-projected costse or strijB. 
Ventral area may be either somewhat flattened and furnished with a carina parting 
two sulci, or it may sJope more or less acutely towards a more or less prominent 
carina, or it may be acute and furnished with a strong hollow carina. Suture-liue 
rather simple ; the superior lateral lobe very broad-stemmed ; none of the saddles 
deep. In the compressed broad-whorled species all the lobes broad-stemmed, and 
the siplional saddle furnished with two well-marked accessory lobes. 
I have included in this genus a retrogressive series of species, and although 
the extreme forms of the series present very different characters, yet the whole 
series is apparently in direct genetic connection (p. 307). Practically-speaking, the 
' County of Dorset. 
