F. R. Cowper Heed — Some Wenlock Sjyecies of Lichas. IL 



preserved specimen (11), which he used chiefly in drawing fig. 5, 

 pi. xxvii his. 



Lichas (Dioeanopeltis ?) Salteri, Fletcher. 



L. Salteri, Fletcher: Q.J.G.S., 1850, vol. vi, p. 237, pi. xxvii, figs. 9,-9a; 

 pi. xxvii bis, fig. 4. 



Lindstrdm ^ records this species from Gotland, and believes that 

 L. laticeps, Angelin (Pal. Scan., 1854, pp. 70, 72, t. xxxvii, figs. 8, 8a, 

 nan t. xxxviii, fig. 5), and L. gibbiis, Angelin (Pal. Scan., p. 71, 

 t. xxxvii, fig. 1, pygidium only), are synonyms. The rows of large 

 tubercles on the glabella and side-lobes are held by Lindstrom to- 

 be the particular characteristic of the species ; and unfortunately 

 no part but the head-shield, and that incomplete, is known from the 

 Wenlock Limestone. It is impossible to feel on safe ground in 

 assigning any of the isolated pygidia of this horizon to L. Salteri, 

 but Lindstrom ^ considers the pygidium figured by Angelin (op. cit. 

 Slip.) as L. gibbus as probably belonging to this species, and describes 

 it as possessing a linear axis narrowing posteriorly, furnished witli 

 about eleven segments, of which the posterior ones are inconspicuous ; 

 a narrow prolongation extends behind it towards the margin. Three 

 small pleura-like ribs are given ofi" on each side from rather in front 

 of the middle of the axis. There is a raised border round the 

 pygidium, and from it short, backwardly directed spines project near 

 the terminations of the ribs. Between the two posterior ones are 

 three pairs of small spines, one of which projects from the axis. 

 It is to be regretted that Lindstrom did not give a figure of this 

 specimen, as Angelin's figure leaves much to be desired, and it is 

 difficult to form an adequate idea of the pygidial characters from the 

 description. 



The old generic designation Trochurus is revived by Lindstrom 

 for this species, and applied also to T. pusillus, Angelin, and 

 T. BucMandi, Milne Edwards (= L. anglicus, Beyrich). Beyrich, 

 however, in 1846 (Untersuch. iiber Trilob.) declared that this name,, 

 which he had instituted in 1845 (Ueber Boh. Trilob., p. 31, fig. 14), 

 should be allowed to drop, as the genus had been founded on 

 a specimen consisting of portions of two distinct trilobites (i.e. a head 

 of Staurocephalus MurcJiisoni combined with a pygidium ofi. speciosiis, 

 Beyr. [= L. pahnata, Barrande]). Barrande (Syst. Sil. Boh., vol. i, 

 p. 603) points out this fact, and also rejects for this reason the 

 specific name L. speciosus, which Beyrich had given in 1845 to the 

 composite form. It accordingly appears inadvisable to revive the 

 name Trochurus under any form. Beyrich himself employed in 1846 

 Goldfuss' earlier name Arges (1839) for his species L. speciosus 

 (= L. pahnata, Barr.), but, as previously pointed out by the present 

 writer,^ this name is preoccupied. 



1 Lindstrom: Gotl. Silur. Crust. Ofv. K. Vet. Akad. Forhandl., 1885, No. 6, 

 p. 60 {Trochurus Salteri) ; List of the Fossils of the Upper Silurian Formation of 

 Gotland, Stockholm, 1885, p. 3 {Trochurus Salteri). 



2 Gotl. Silur. Crust. Ofv. K. Vet. Akad. Forhandl., 1885, p. 60, 



3 Q.J.G.S., 1902, vol. Iviii, p. 60. 



