6 



BRITISH FOSSILS. 



restored the name Crt/ptonymus, under which Eichwald at first described several varfetief 

 of the common Asaphi of the Russian Silurian Rocks. Subsequently, aware of his error, 

 he restricted Cryptonymus to such trilobites as the Calym. variolaris, Brong., including the 

 C. punctatus, and some forms of Cybele. But, though thus marking out the group he 

 intended, he gave no description of the amended genus ; besides which he was now applying 

 the name to a totally different set of fossils to those for which it was originally intended. 

 Under such circumstances it is impossible to retain his name in opposition to the genus 

 clearly indicated, though not sufficiently described, in Emmerich's scientific arrangement, 

 1845. The latter name has been adopted, and the typical species fully characterized by 

 Professor M'Coy (Synopsis Sil. Foss. Irel., 1846). The genus Encrinurus has a nearly 

 universal range, being found in Silurian rocks from Russia to North America, and from 

 the Arctic regions to Australia ; and it has rather an extensive geological distribution, 

 being found in Lower and Upper Silurian, and in the Devonian strata of Germany. 

 Cromus, Barrande, a Bohemian fossil, is probably of the same genus ; it has, however, four 

 lateral lobes to the glabella, instead of three. 



Stt!T. Entomoliihus paradoxus, Linnaeus, 1759, Act. Reg. Acad. Sc., Holm., p. 22. t. 1. 

 f. 2. Tril. punct, Briinn., Kjobenh, Sellsk. Skrivt. nye Samml. 1. 394. Entomostrac. 

 punct, Wahl. (1821), Act. Soc. Sc. Ups. v. viii. 32. t. 2. f. 1. — tail only. Calym. variolaris, 

 Brongn., Crust. Foss., t. 1. f. 3 A. (not B.) Cal. punctata, Dalm. Pal. 47. t. 2. f. a, b. 

 Murch. Sil. Syst. (1839), pi. 23. f. 8. Phacops variolaris, Emmrich. Diss. (1839), 20. 

 Asaph, tuberculatus, Buckl. Bridgw. Tr., pi. 46. f. 6. Encrinurus punct., Emmr. (1845), 

 Neues Jahrb. 42. Encrinurus Stokesii, M'Coy (1846), Syn. Sil. Foss. Irel., t. 4. f. 15. 

 Pal. Foss. Woodw. Mus. (1851), p. 158. E. punctatus, Corda (1847), Prodr. Tril. Bohm. 

 91. fig. 55. bona. Cybele punct., Fletcher, Quart. Geol. Jour. (1850), vol. vi. ph 32. f. 1-5. 



E. ovatus, biuncialis ; glabella clavatd convexa sed parum infiata tuberculosa ; tuberculis 

 anticis paullo majoribus, in arcu dispositis, sulcis glabellaribus brevibus vix inter tuberculos 

 magnos visis ; genis convexis profunde marginatis, tuberculis sub oculo valde elevate angusto 

 colhcatis, angulis spinosis ; hypostomate basi subcompresso, rostro apiculato; thorace axi 

 pleuris curvatis paullo angustiore, segmento septimo decimoque brevi-spinosis ; caudd longe 

 triangulata, lateribus ante apicem nunc planum recurvum, nunc dejlexum obtusiorem contractis ; 

 costis lateralibus 8 obliquis, ad apices prominulis ; axi nec convexo, annulis crebris per medium 

 omnino obliteratis, tuberculis quinque vel sex in serie longitudinali dispositis. 

 Var. a. Calcareus. — Caudd in mucronem planum seu recurvum producto. 

 Var. j8. Arenaceus. — Caudd apice deflexo obtusiori. 

 The original Swedish species appears certainly to differ in no respect, so far as the tail 

 is concerned, from that common in the Dudley limestone ; the tubercles on the 

 lateral ribs, on which so much stress has been laid, being always present, either at 

 the origin of the rib or on its surface. And the species is pretty well represented 

 by M. Corda from Swedish specimens. The thorax rings we have not seen from 

 Sweden, but they are tuberculate as ours are, according to the figure above 

 quoted. 



The variety we have called arenaceus appears to differ only in the abrupt ending of 

 the tail, which, instead of being horizontal and drawn out into a mucro of variable 

 length, as in the limestone specimens from Dudley and elsewhere, is deflexed and 

 blunt. But the specimens from the Caradoc and Llandeilo sandstones agree so well 

 in all other particulars, the tubercles collected round the eye, the number of ribs 

 and tubercles on the tail, &c. &c., that it cannot be separated as more than a 

 variety. Its name indicates its usual habitats, and the deficient development of the 

 tail may be connected with the deficient supply of calcareous matter. Upper 

 Caradoc specimens are almost always smaller; occasionally, as at Bogmine, in 

 Shropshire, they are of full size. Some Ludlow specimens have the glabella nar- 

 rower, and but four tubercles down the axis of the tail. 



2. E. PUNCTATUS. Briinn. sp. PI. 4. f. 1^-16. 



