124 PERMIAN FOSSILS. 4 
and Pentamerus, and certain Orthises.1 The socket-plates appear to be in general 
only slightly developed. 
The fissure in Spiriferide possesses a variable character, being closed by the 
deltidium in the typical genus; also in certain species of Zrigonotreta (T. rostrata and 
T. speciosa) ; but it is well known to be openin others. It appears to be closed, when 
the shell is young, in Zrigonotreta cyrtena, and afterwards to become open: on the 
contrary, in Zrigonotreta undulata it is open when young, and closed when old. 
Spiriferide are not generally foraminated: two or three genera are character- 
istically so, and another only thus partially. In Sperifer the foramen passes through 
the deltidium :3 in #e/z7a it is complete, and situated at or near the point of the umbone, 
as in Terebratula: while in Atrypa (reticularis) the same part is similarly foraminated ; 
but only in certain varieties. 
The present family differs remarkably from its equivalent and associated groups in 
rarely exhibiting traces of the vascular system; as the only specimen I have seen 
displaying them is the one represented in fig. 6c, Pl. IX. 
The histology of Spiriferide offers certain modified characters, which, however, 
are not of such a nature as is generally supposed. Dr. Carpenter has noticed 
“perforations very well marked in Spirifer Walcott of the Lias, while they are absent 
in Spirifer cuspidatus, and another mountain-limestone species, and in a species from 
the Devonian formation of Hudson’s Bay.”* These perforations or punctures have 
been long known to me, as occurring in certain Permian species; and they have been 
recently noticed by Dr. de Koninck, who says, “in the genus Spirifer several species 
are known to have the shell perforated, as in certam Terebratule: these species 
constitute the genus Spiriferina of M. dOrbigny: the Spirifer cristatus, Schl., is in 
this case: this species I have found among the fossils of M. Roberts;? and as none of 
the perforated Spirifers have yet been found im the carboniferous rocks, we are 
warranted in concluding that the Palaeozoic fossil beds of Spitzbergen belong to the 
Permian epoch.° 
But unfortunately for Dr. Carpenter’s observation, and Dr. de Koninck’s’ con- 
1 Vide Ann. and Mag. of Nat. Hist., vol. xviii, p. 86, 1846. 
2 This character of the fissure is supported by some unpublished figures of Trigonotreta cyrtena executed 
in lithograph by Mr. T. Davidson. 
3 In Spirifer heteroclytus the deltidium is convex or ridge-like on its inferior half, and concave or 
furrowed on its upper half: the foramen is situated at the base of the furrow, and passes behind the ridge. 
4 Report of the Fourteenth Meeting of the British Association, p. 18, 1845. Dr. Carpenter states that 
Mr. Morris had noticed the like difference in other Spiriferide. 
5 M. Roberts’s fossils were collected at Spitzbergen, among which, according to Dr. de Koninck, are 
Trigonotreta undulata and Strophalosia Canerini. 
6 Vide Bulletin de la Soc. Géol. de France, 2™ série, t. vi, Seance June 2, 1849. 
7 In some specimens of a carboniferous Trigonotreta collected in Belgium, and given me by Mr. T. 
Davidson, the punctures are as visible as in 7”. cristata. I believe the specimens referred to have been 
identified by Dr. de Koninck with the last species; but they are certainly distinct. 
