BRITISH FOSSILS. 



Decade VII. Plate II. 



CHEIRURUS BIMUCRONATUS. 



[Genus CHEIRURUS. Beyrich. (Sub-kingdom Articulata. Class Crustacea. 

 Order Entomostraca. Tribe Trilobitse or Palseadae.) Head strongly trilobed ; glabella 

 Mvith. three lateral lobes, the basal ones circumscribed ; eyes facetted ; facial suture ending 

 on the external margin; a rostral shield: Barrande. [Cheeks scrobiculate] ; hypostome 

 inflated, oblong, truncate, with a marginal furrow and lateral auricles; thorax of 11 

 joints, the pleurae strongly nodular as far as the fulcrum, the ends free and pointed; 

 tail of few, 3 or 4, segments, free at their ends.] 



Diagnosis. C. grandis ; glabella superne latiori, sulco frontali et ocu- 

 lari obliquis prope medium glahellce terminatis ; lobis inferis trigonis {cetate 

 rotundioribus) sejunctis ; genis glabella angustioribus, oculis medianis, 

 spinis posticis parallelis ; thorace pleuris trituberculatis ; cauda parvuld, 

 utrinque pleuris tribus subcequalibus ad basin brevisulcatiSj apicibus robustis, 

 arcuatis. 



Synonyms. Var. a. Bimucronatus — caudd mucrone centrali nullo. 



Calymene speciosa [Dalman (1826), Pal., pp. 58, 76 ?] Hisinger(1840), 

 Lethaea Suecica, Suppl. 2d. t. xxxix. fig. 2. Paradoxides bimucronatus, 

 MuRCHisoN (1839), Sil. Syst., pi. 14. fig. 8,9. Milne Edwards (1840), 

 Crustac, vol. iii. p. 343. Arges bimucr. GtOldfuss (1843), Neues Jalirb. 

 544. Cheirurus bimucronatus, Beyrich (1845), iiber einige Bohmische 

 Tril., p. 18, 19. Cheir. ornatus (Dalm.), ^, bimucronatus, Bronn. Ind. 

 Palseont. (1848), 1. 286. C. speciosus, Salter (June 1848), Memoirs 

 Geol. Survey, vol. ii. pt. 1. pi. 7. fig. 4, 5, 6. Ceraurus Williamsii, M'Coy 

 (Dec. 1849), Ann. and Mag. Nat. Hist., p. 408, Pal. Foss. Woodw. Mus. 

 (1851), pi. IF. fig. 13. 



Var. iS. Centralis, fig. IG.—caudd mucrone centrali brevi, Mem. Geol. 

 Surv., 1. c. fig. 7. 



The subject of our present notice received some degree of illustra- 

 tion in the second volume of the Memoirs of the Geological Survey, 

 and we need not repeat here the figures which indicate the large 

 size to which the species grew, but take advantage of a beautiful 

 and nearly perfect specimen, found near Aymestry, and lent to us 

 by the Rev. T, T. Lewis, whose valuable labours are so frequently 

 [YiLii.] 7 b 



