654 



TRILOBITES OF THE UPPER SILURIAN ROCKS. 



abundantly in the latter. It is, however, generally characteristic of the Upper Silurian Rocks. 

 Together with the Asaphus caudatus, it is one of those trilobites which have the widest geo- 

 graphical range, occurring in North America, Norway, Russia, and in various parts of France, 

 Germany, and Poland. To these localities I may add Southern Africa, where, as above stated, 

 it has been found associated with the Homalonotus Herschelii, and other fossils of the Upper 

 Silurian Rocks. 

 Asaphus, Brongniart. 



Gen. Char. — " Corps large et assez plat; lobe moyen saillant et tris distinct. Flancs ou lobes 

 lateralis ay ant chacun le double de la largeur du lobe moyen. Expansions submembraneuses 

 depassant les arcs des lobes latdraux. Boucher demi-circulaire portant deux tuberculea 

 oculiformes reticules ? Abdomen divise en huit ou douze articles." 

 Asaphus caudatus, f. 8«. Brongn. 



This figure is given to show the form of the tail of the species figured by Brongniart and 

 other naturalists as the true Asaphus caudatus, which differs from our large figure 8, in ex- 

 hibiting a central lobe without tubercles, a very distinct separation of the abdomen from the 

 caudal portion, and the termination of the lateral ribs of the former in points. 

 Loc. In great abundance throughout the Upper Silurian Rocks, {Ludlow and Wenlock for- 

 mations), being nearly as prevalent as the Calymene Blumenbachii. 

 Asaphus tuberculato-caudatus, (n.s.), f. 8. 



Spec. Char. Shield anterior part oval, posterior strongly margined, sides extended to the 

 sixth rib and terminating in sharp points. Head covered ivith small tubercles, central lobe 

 having 5 protuberances, 4 of which, somewhat resembling ribs, lie between and beloiv the eyes ; 

 the fifth is large, expands laterally, and advancing to the anterior edge of the shield is 

 marked through half its length by a furroiv. Eyes crescent-shaped, conical, composed of many 

 lenses 1 . Body, each rib of central lobe ornamented by a large tubercle on either side. Caudal 

 portion, ribs tuberculated like those of the body, terminated by a sharp tail. 



I have ventured to separate this species from the A. caudatus, Brongn., because every rib 

 of the central lobe of the body and caudal portion (in all twenty-three) is flanked by a large 

 stud or tubercle. It further seems to differ in its head being enriched with tubercles, and in 

 having an additional frontal protuberance ; while the body and caudal portion which are almost 

 inseparable in our species, are very sharply divided in A. caudatus, Brongn. 



This species resembles A. limulurus of the United States, in having a small tuberculated 

 central lobe; but the latter has a fine pointed tail like our A. longicaudatus, PI. 14. figs. 11, 12, 

 13 and 14, and its ribs terminate laterally in reflected spines. (See Green's Monograph, p. 48. 

 and cast 16.) 

 Loc. Dudley. 



Asaphus ( Olenus) jlahellifer f, Steininger ; Trans. Soe. Geol. de France, torn. i. pi. 21. f. 10. 



The caudal termination of this fan-tailed species, found by Dr. Lloyd, in the Wenlock Lime- 

 stone, is in the Museum of the Ludlow Society. A good drawing of it was sent to me by 

 Professor Phillips, and I have since seen the original. It somewhat resembles A. laticauda, 

 Brongn. PI. 3. f. 8., and also A. laciniatus, Dalm. t. 6. f. 1., but is most probably identical with 

 the A. ( Olenus) Jlahellifer of Steininger from the Eifel. Although I have not figured this 

 curious fragment, I may observe that similar caudal remains are said to occur in South Devon. 



1 The use of these lenses in horizontal vision, and of which there are at least 400 in Asaphus caudatus, is 

 beautifully described in Dr. Buckland's Bridgewater Treatise, p. 399., and has been before adverted to p. 647. 



