BRITISH FOSSILS. 



Decade II. Plate VIII. 



CALYMENE TUBERCULOSA. 



[Genus CALYMENE. Brongniart. (Sub-kingdom Articulata. Class Crustacea. Order 

 Entomostraca. Family Trilobitse). Axis distinct; glabella lobed, narrower anteriorly ; 

 facial suture dividing the posterior head angles, submarginal in front ; a rostral shield ; 

 eyes supine (with a thin cornea ?) ; thorax of 13 rings, formed for rolling.] 



Diagnosis. C. lata^ depressa, alutacea; margine frontali capitis pro- 

 ducto recurvo, genis gibbosis, glabella depressd ; thorace axi angusto, pleuris 

 planis usque ad fulcrum^ quod ad dimidium anterius, ad tertium posteriusy 

 positum est ; caudd lata, superne depressd, lateribus abrupte deflexis ; axi 

 conico, subplano, 7-8 annulaio, costis lateralibus 5, planis^ sulcis ocutis. 



Synonyms. C. Blumenbacliii vera'^ a. tuberczdosa, Dalman (1828), 

 p. 36? (not tab. 1, f. 2). C. Blumenb., var. a. tuberculosa. Hisinger 

 (1837), Lethaea Suecica, 10? (not tab. 1, f. 3). C. Blumenb., Murchison, 

 (1839), Sil. Syst., pi. 7, f. 5 only. C. tuberculosa, Salter (June, 1848), 

 " Memoirs of Geol. Survey," vol. ii. part 1, pi. 12. 



Almost every author who has written on Calymene Blumenbachii has 

 hinted his belief that two or more species were to be recognized among 

 its protean forms ; yet, except Colonel Portlock, who separated the C. 

 hrevicapitata in his report on the fossils of Tyrone, no one has done -more 

 than point out varieties. An extended examination of very numerous 

 specimens convinced us that three distinct species were known in Eng- 

 land, and their characters were detailed in the 2nd volume of the 

 " Memoirs of the Geological Survey." Still further investigation of 

 intermediate forms has shaken this opinion again, and we are at present 

 wholly in doubt whether the striking differences about to be pointed out 

 mark only a distinct variety, or are of specific value. At all events, in 

 giving a typical species of this genus, we would rather present the 

 reader with a new and well-marked form, than with one so familiar as 

 that of the famous " Dudley fossil." 



Description. — Length, about 2i inches, width, H inch. Whole sur- 

 face equally and minutely scabrous. General form broad for the genus, 

 not much attenuated posteriorly, depressed. Head short, wide ; the 

 [ii. viii.] 2 H 



