Vol.58.] | MR. F. R. C. REED ON THE GENUS LICHAS. "6S 
Trocnurus, Beyrich, 1845 (‘Ueb. Béhin. ‘Trilob.’ p. 31). This name was 
originally applied to a composite and artificial species consisting of the 
head of “Stcurocephalus Murchisont and the pygidium of Lichas. This 
heterodox species was called Jr. speciosus, Beyrich (Coc. eit.). But in 
1846 Beyrich recognized his error (‘ Untersuch, ib. Trilob.’ p- 10) and 
declared that. the genus did not exist. It seemstherefore desirable to drop 
the name altogether; but Lindstrom has recently (Ofv. K. Svensk. Vet.- 
: Akad. Forhandl. 1885, No. 6, p. 60; and ‘ List Foss. Up. Silur. Gotland’ 
1885, p. 3) revived it in a wider and slightly different sense, giving L. Salter, 
Fletcher and L. Buchklandi, M.-Edw. (=L. anglicus, Beyr.) as examples. 
Uranicnas, Delgado, 1892 (Comm. d. Trab. Geol. Portugal, ‘ Fauna Silurica 
de Portugal’ p- 5). Type, U. Ribetrot, Delgado, 1892. 
The palzontological value of the above groups as subgenera or 
genera is examined in a later portion of this paper; but it may 
here be remarked that several well-known and more or less widely 
accepted names must be dropped, because of their pre-occupation or 
for other reasons given above. Such are Arges, Metopias, Nuttainia, 
Platymetopus, Platynotus, and Trochurus. The advisability of 
substituting new names in the place of those chosen by Corda is 
open to question, since Barrande revised Corda’s species, and the 
change might lead to confusion. 
The characters of the original type-species on which each group 
was founded have so frequently been Jost sight of in assigning other 
or subsequently discovered species to a subgenus or genus, that it 1s 
well to give a list of these type-forms for reference in all cases. 
As an example of the expansive interpretation of the characters of 
a group and the gradual enlargement of its boundaries so as to 
include very diverse species, the group Arges may be mentioned, 
of which the original species is Arges armatus, Goldfuss,’ with 
highly specialized Characters which are found in scarcely any of the 
other forms commonly attributed to this subgenus. 
The following is a hst of the type-species, the old subgeneric 
names (excluding only synonyms) being retained for the present :— 
Acanthopyge Haueri (Barrande). | Homolichas depressus (Angelin). 
Arctinurus Boltoni (Bigsby). FHoplolichas tricuspidatus (Beyrich). 
Arges urimatus, Goldfuss. Leiolichas illenoides (Nieszkowski). 
Ceratolichas gryps, Hall. _ Lichas laciniatus (Wahlenberg). 
Conolichas equiloba (Steinhardt). Metopias Hiibneri, Eichwald. 
Corydocephalus palmatus (Barrande). Oncholichas ornatus (Angelin). 
Craspedarges Wilcannie, Girich. Platopolichas avus (Barr.). 
Dicranogmus simples (Barrande). Platylichas margaritifer (Nieszk.). 
Dicranopeltis scabra (Beyrich). Platymetopus lineatus, Angelin. 
Echinolichas Eriopis (Hall). Terataspis grandis, Hall. 
Hemiarges wesenbergensis (Schmidt). Uralichas Ribeiroi, Delgado. 
The references to the original and most important descriptions of 
the above species have already been given. 
* Nova Acta Acad. Cs. Leop.-Carol. vol. xix, pt. i (1839) p. 355 & pl. xxxiii, 
figs. la, 1b, le (non 1d, 1.2). 
