CLASSIFICATION OF THE BRACHIOPODA. 83 



Geol. range. — The exact period at which the punctated Spirifers first appear is still 

 doubtful ; they are known from the Devonian epoch to the upper Lias, above which no 

 example has been as yet recorded. 



Examples : Spiriferina rostrata, Schl., sp. ; Tessoni, DeslongcJiampsii, and Munsteri, 

 Dav. ; oxyptenis and sif/nensis, Buv. ; cristafa, Schl. sp., &c. ; Haueri and Emerici, Suess. 



Section B. — Cyrtia, Balman, 1827.^ 



Type—G. expokrecta, Wahl. Int., PI. VI, figs. 61, 62 (63 and 64?). 



Spibifer, of the generality of Authors. 

 Cyrtia, Balman, TfOrhigny, M'Coy, &c. 



Shell somewhat trigonal ; valves convex ; hinge line nearly as long as the width of the 

 shell, articulating by means of teeth and sockets ; dental or ventral valve very deep, 

 more or less pyramidal ; beak straight, or slightly recurved ; area wide and triangular ; 

 fissure entirely covered by a convex pseudo-deltidium in one piece, generally perforated 

 extremely close to the beak by a circular foramen ; sometimes this deltidium is longitudi- 

 nally depressed along its centre, from the extremity of the beak to within a variable 

 distance of the cardinal edge ; at the extremity of this shallow groove is seen a small cir- 

 cular aperture, which up to a certain age afforded passage to pedicle muscular fibres ; tke 

 socket or dorsal valve is very slightly convex, and is supposed to have been furnished 

 internally with spiral cones ; in the larger valve a mesial longitudinal septum extends 

 from the extremity of the fissure to a short distance of the margin, and to the sides of 

 which the dental plates converge, and are united after having formed the fissure walls. 



Ohs. Since the genus Cyrtia has been admitted by a number of Palasontologists, it 

 may be desirable to investigate the grounds for such a conclusion. Dalman's diagnosis 

 is unsatisfactory, and equally applicable to several species of his genus Belthyris -. we are 

 informed that in Cyrtia the shell is inequivalve, larger valve raised into a semi-cone or 

 half pyramid, with the hinge side vertically flat, foramen circular, hinge line straight. 

 — Examples. C. exporrecta and trapezoidalis. 



The shells here mentioned are varieties of one species, well known in England, which 

 must therefore be considered as the type of the section, and from it our diagnostic 

 has been extended. It should also be remarked, that a microscopic examination by 

 Dr. Carpenter, has proved its shell structure to be fibrous, impunctate, and similar 

 in character to that of Spirifer proper {Striatus). The only differences at present known 

 consist in a slight modification in the character of the deltidium, and presence of a circular 

 perforation for the passage of a pedicle ; likewise in the direction of the dental plates, and 



^ Petrefacta suecana, in ' Kongl. vet. Acad. Handl.,' 1827. 



^ This character is beautifully displayed in some Devonian species found in Belgium and China. 



