Chap. X.] 
UPPER SILURIAN CEPHALOPODS. 
233 
f. 3, 0. canaliculatum, PI XXVIII. f. 3, are rarer Wenlock species ; whilst O. 
distans, PL XXVI. f. 4, O. subgregarium, PL XXVII. f. 2, and O. imbricatum, 
PL XXIX. f. 7, are among the less abundant Ludlow fossils. 
Orthoceras tracheale, PL XXXIV. f. 6, and 0. (Tretoceras ?) semipartitum, 
f. 5, though not very common, are characteristic of the uppermost Ludlow or 
Tilestones, — as well as 0. bullatum, above noticed, which occurs in the greatest 
abundance in every locality of the Upper Ludlow rock. 
The same distribution is observable in the other genera ; for while certain spe- 
cies of Phragmoceras and Lituites are peculiar to the Wenlock, or the Lower 
Ludlow, but few range throughout. Phragmoceras ventricosum *, PL XXXII., 
however, which has been already mentioned, is one of these last : it is frequently 
found at Malvern, in Wenlock limestone, and also at Leintwardine, Shropshire, 
in Lower Ludlow, where also Ph. pyriforme, PL XXX. f. 1-3, abounds. 
This species, being straight instead of curved, has usually been regarded as a 
distinct genus, Gomphoceras. Phragmoceras arcuatum, PL XXXI. f. 3, and 
Ph. intermedium, PL XXX. f. 4, are also Lower Ludlow forms. Ph. nautileum, 
PL XXXI. f. 1, 2, and Ph. compressum, f. 4, are found in Wenlock shale ; the 
last is even a Llandovery fossil. 
Lituites articulatus, Sow., is found both in'Wenlock and Ludlow rocks; L. Bid- 
dulphii, PL XXXI. f. 5, in Wenlock limestone. Lituites giganteus, PL XXXIII. 
f. 1, 2, 3, is one of the finest fossils from Leintwardine and Malvern ; and L. 
tortuosus, of which a fragment is figured, f. 4, is found in the black nodules of 
the Wenlock Shale near Welshpool, and also at Dudley. 
The curious genus Ascoceras, of which Barrande has described several 
species from the Bohemian basin, has been found in the uppermost Silurian 
rocks of Britain. The species differs but little from the common Bohemian 
form ; it has been called A. Barrandii by Mr. 
Salter. There are specimens from Usk, Lud- Fossils (63). 
low, and Malvern in the Museum of Practical An Upper Ludlow Cephalopod. 
Geology; and it may prove to be common. 
This fossil seems more nearly allied to the 
curious genus Tretoceras above mentioned 
(p. 213: Diploceras in the former edition) 
than might be at first supposed. 
To complete the catalogue of the Upper 
Silurian fauna, a brief sketch must be given 
of its Annulose animals, the Worms and 
Crustaceans, as well as of the remains of Fishes 
which have been discovered. 
Cornulites serpularius (see PL XVI. f. 3-10) Ascoceras Barrandii, Salter 
is still, as in the Llandovery rocks, the prin- (Quart. Journ. Geol. Soc. 1856, 
cipal Annelide, and, though more frequent in ^^2LSmJ^ 
the Wenlock Limestone, is not rare m the Lud- Ludlow rock, 
low rocks. The finest specimens are from the 
Wenlock Limestone of Ledbury; but at Dudley, Cornulites are found attached 
to shells, in groups of three or four together, like Serpulae ; and they occur in 
profusion on the hard and sea- worn surfaces of the Ludlow rock at Marloes Bay 
in Pembrokeshire, in masses a foot in diameter. Tentaculites ornatus, PL XVI. 
f. 11, abounds in the Dudley limestone ; whilst a small species, T. tenuis, f. 12, 
occurs in the Upper Ludlow rock. The place of the latter is sometimes taken 
* [This fine Silurian species can scarcely be the Orthoceras ventricosum of Steininger.— J. W. S. 1859.] 
