316 Mr. J. Morris on the genus Siphonotreta. 



form was also first noticed by Eichwald in 1829 as a Crania (C. 

 sulcata, C. unguiculata), which he afterwards (1843) placed under 

 Terebratula* ; subsequently however M. de Verneuil, in the se- 

 cond volume of the great work on Russia f, recognized the dif- 

 ferences which separated these fossils from Crania and Terebra- 

 tula, and gave them the very characteristic name of Siphonotreta, 

 describing two species, S. unguiculata and S. verrucosa. Since 

 the publication of the work on Russia, four additional species of 

 the latter genus have rewarded the researches of Hern. v. Vol- 

 borth and other Russian geologists, which are fully described, as 

 well as those previously known, in the monograph by Dr. Ku- 

 torga above alluded to, and from which is extracted the following 

 synopsis of the principal characters of the genera included by 

 Dr. Kutorga in the family of Siphonotretese. 



SiphonotretejE, Kutorga. 

 A. With a tubular closed sipho. 



a. The external siphonal opening passes from the apex towards the 



anterior margin. 



1 . Siphonotreta, De Verneuil. 



S. unguiculata, Eichw. sp. S. conoides, Kut. 



S.fomicata, Kut. S. tentorium, Kut. 



S. verrucosa, Vern. S. fissa, Kut. 

 S. aculeata, Kut. 



b. The siphonal opening is directed from the apex towards the dor- 



sal margin. 



2. Schizotreta, Kutorga (Orbiculoidea, D'Orbigny). 

 Opening narrow, slit-like ; no area, nor mark of deltidium. 



Sch. elliptica, Kut. 



3. Acrotreta, Kutorga. 



Opening elongated, oval ; area triangular and flattened, with a 

 deltidium-like furrow. 



A. subconica, Kut. A. recurva, Kut. 



A. disparirugata, Kut. % 



B. With a furrow-like sipho, opened on the whole hinge area. 



4. Aulonotreta, Kut. (Obolus, Eichw.; Ungula, Pander). 



A. polita = O. Apollinis, siluricus, ingricus, Eichw. ; Orthis un- 

 gula, Von Buch. 

 A. sculpta = 0. antiquissimus? Eichwald. 



" The Siphonotretese are free, unattached Brachiopods J, whose 



* Beitragen zur Kenntniss des Russ. Reichs, 1843. 



f Russia and the Ural Mountains, by Sir R. I. Murchison, 1845, vol. ii. 

 p. 286. 



J Dr. Kutorga alludes to the shells not being solidly attached by either 

 of the valves. 



