CEPHALOFODA. 
There were at least three kinds of pro-ostracum in the 
family Belemnitidee. 
A. In many Belemnites the extension of the conotheca seems 
to run out in one simple broad BIG, Fig. 3, as in B. hastatus 
from Solenhofen. 
B. In Belemnites Puzosianus, D’Orbigny, the pro- -ostracum 18 
very thin, and apparently horny or imperfectly calcified in the 
dorsal region, supported laterally by two long, narrow, parallel, 
calcareous plates, Fig. 4, as in B. Puzosianus from the Oxford 
clay. Professor Huxley considers this difference between the 
pro-ostraca of generic importance. 
©. The third kind of pro-ostracum is exhibited by Orthocera 
elongata, De la Beche, the type of the genus Xiphoteuthis, 
Huxley ; it is calcareous, and is composed of concentric lamelle, 
each of which consists of fibres disposed perpendicularly to the 
plane of the lamella; the phragmocone is very long and narrow, 
and the guard cylindroidal. 
Professor Huxley suspects that a thoroughly well-preserved 
specimen of Belemnoteuthis will some day demonstrate the exist- 
ence of a fourth kind of pro-ostracum among the Belemnitide. 
The genera in the family are:—1, Belemnites ; 2, Belemnitella ; 
3, Aiphoteuthis ; 4, Belemnoteuthis ; 5, Plesioteuthis ; 6, Celoeno ; 
7, Beloptera ; 8, Belemnosis ; 9, Conoteuthis; and ? Helicerus. 
“‘The A anthoteuthes of Munster, so far as they are known 
only by hooks and. impressions of soft parts, may have been 
either Belemnites, or Belemnoteuthis, or Plestoteuthes, or may have 
belonged to the genus Celeno.” (Huxley.) 
The genus Belopeltis, Voltz, was founded on the pro-ostraca 
of Belemnites, species of which were unknown. 
The genus Actinocamax, Miller, was founded on the guard 
of Belemnites and Belemnitella, the upper parts of which had 
decayed, and thus presented no alveolar cavity. 
ORDER II.—TETRABRANCHIATA. 
Famity I.—NAvTILIDz 
(including Famity II.—ORTHOCERATID 2). 
DIVISION a@.—AIR-CHAMBERS CONFINED TO ONE PART OF THE 
SHELL, 
ASCOCERAS, Barrande, 1846.* 
Etymology; askos, « leathern bottle, and ceras. 
* At p. 185 Mr. Woodward refers to M. Barrande’s second volume of the “ Cephalo- 
pods of Bohemia.” The Ascoras, Glossoceras, and Aphragmites are here described. 
