ANIMALS. 113 



more or less diverging dental plates ; and a median sinus. Small valve with two long 

 more or less diverging socket-plates.^ 



Isorhynchus embraces, with perhaps the exception of the so-called Spirifer Tcheffkini 

 all the species forming the section Equirostres of De Verneuil's Abnormal Spirifers. 

 Although placed in the present family, I am not decidedly of opinion that the collo- 

 cation is a correct or natural one : there are obviously many difficulties preventing the 

 proximate affinities of the genus being satisfactorily determined. Should Spirifer 

 Tcheffkini really be a congeneric form, no very serious argument could be urged 

 against Isorhynchus being considered one of the Strophotnenida, and closely allied to 

 Platystrophia ; but its foramen, dental and socket-plates, and general form are strongly 

 in favour of its being placed in Hypothyrida ; while, on the other hand, it has apparently 

 some relationship to certain genera {Betzia and Atrypa) of Spiriferida. 



Isorhynchus appears to have been one of the earliest created groups, being found 

 in, and apparently confined to, the lowest Silurian beds of Russia and Norway : this 

 circumstance, and its possessing characters which seem to relate it to three widely 

 distinct families, render the genus of the utmost importance in a philosophical or 

 morphological point of view. 



Possessing no precise information on the genus Uncites proposed by De France, 

 and having nothing to add to the description I have elsewhere published of Penta- 

 merus^ I purpose in the next place to proceed with the remaining genus requiring 

 consideration in connexion with the present family. 



Genus Camarophoria^ King, 1844. 

 Tekebkatula, Auct. 



Diagnosis. — Hypothyriform ; coarsely fibrous, and minutely punctured ; with a 

 small open fissure. Large valve with the dental plates conjoined at their upper margin, 

 forming an arch-shaped process, which is attached by its crest to the (ventral) medio- 

 longitudinal plate. Small valve with two long slender processes striking off from the 

 centre of the crural base — a horizontal plate, — and curving up towards the opposite valve; 

 also a spatula-shaped process originating a little below the latter, projecting considerably 

 forward with an upward curve, and supported by the (dorsal) medio-longitudinal plate. 



Type, Terebratula Schlotheimi, Von Buch. 



^ The above diagnosis has been drawn up both from my own observations on some specimens kindly 

 presented to me by M. de Verneuil, and the description published by him of the corresponding group, 

 Equirostres, in Geol. Russ., vol ii, p. 128. 



2 Vide Annals and Magazine of Natural History, vol. xviii, pp. 83-7. 



3 Etym., Ka/jiapa (an arched) chamber ; foipetv, I carry. I originally spelled the name Camerophoria, 

 but I feel much pleasure in adopting the correction made in it by M. Herrmannsen, in his ' Indices Generum 

 Malacozoorum Primordia,' p. 161, 1846. 



