SPIRIFER^ OF THE CHEMUNG GROUP. 243 



sinus, are conspicuously marked by fine regular radiating striae, and, 

 in rare examples, these have been observed to be cancellated by con- 

 centric striae. 



Little is known of the interior of the shell, beyond the presence of 

 strong teeth and straight diverging dental lamellae. 



The species presents considerable variety in its form and proportions; but there 

 is usually little difficulty in distinguishing it by the external characters, from any 

 other species in this formation. In its more rotund forms, it approaches the /S. 

 granulifera ; but the presence of longitudinal striae may usually be reco"-nized 

 in the ca.sts, while the broad rounded mesial fold without a depression, is a dis- 

 tinguishing feature. 



Geological formation mid localities. This species has been found in Schoharie 

 and Delaware counties (New- York), several hundred feet above the base of the 

 Chemung group. Fine robust specimens occur near Cortlandville in Cortland 

 county, and a more delicate variety in the greenish shales north of Elmira. The 

 stronger forms, with extended cardinal angles, occur on Cayuta creek in Tioga 

 county. 



Spirifera di!«jancta. 



PLATES XLI & XLII. 



Spirifera dUjnncta .- Sowebbt, Trans. Geol. Society, 2d series. Vol. v, pi. 68. f. 8; pi. 54, f. 12, 13. 1840. 



" calcarata: Id. lb., pi. 53, f. 7. 



" externa : Id. lb., pi. 54, f. 11. 



<< gigantea : Id. lb., pi. 55, f. 1 - 4. 



'• inornata: Id. lb., pi. 68, f. 9. 



<• protenta : Phillips, Pal. Foss. of Cornwall, Devon & West-Somerset, pa. 69, pi. 28, f. 118 



'• calcarata k. S. diijuncta : Id. lb., pi. 29, f. 128, 129. [1841. 



ditjuncla : Id. lb., pi. 30, f. 129. 



•■ gigantea .- Id. lb., pi. 30, f. 130. 



•• grandava : Id. lb., pi. 80, f. 131. 



<■ dittani : Phillips (not Sowebbt), lb., pi. 29, f. 127. 



" verneuili : Mubchisos, Ball. Soc. Geol. France, Vol.11, pa. 262, pi. 2, f. 8. 1840. 



" archiaci : Id. lb., pi. 2, f. 4. 



"^ /ontdoW ; Id. lb., pi. 2, f.2. [1845. 



Spirxfer ditjunctut : Murchison, Dk Veenecil and KBTSEKLiNO.Geol. Russia, Vol. 2, pa. 157, pi 4, f. 4 

 <• archiaci : Id. lb., pi. 4, f.6. 1845. [1845. 



" murchisonianut' : De Koninck, De Veenedil & Ketseelino, Geol. Russia, Vol.2, pi. 4, f. 1. 



• I have cited the synonymy to a great extent from Mr. Davidson's British Devonian Brachiopoda, 

 where the Spirifera murchUonianm ( Db Koninck) is given as one of the synonyms of S. disjunda. 

 I have not observed the explanation which allows this species to be a synonjrm of S. disjunda, and at 

 the same time a Cyrtia, Otrtina (Davidson, Quarterly Geological Jouriial, Vol.ix, pa. 355, pi. 15, 

 f. 6 - 9); but it appears to me that the species figured in the Geology of Russia is distinct from the 

 Chinese specimens figured by Mr. DATiDSOir. 



