RAYMOND: NEW AND OLD SILURIAN TRILOBITES. 7 
back, narrow axial lobe, and nine segments in the thorax. The 
profiles of both shields are rather flat but uniformly convex curves. 
(See especially Holm, Bihang Kogl. Vet. akad. Handl., 1883, 7, pl. 4, 
f. 1-12). Holm was not able to see any value in this genus, pointing 
out that the only real characteristic brought forward by Burmeister 
and by Angelin was the presence of genal spines, and the species with 
genal spines are so highly variable among themselves as to suggest 
that this character in itself does not denote any real relationship. It 
seems, however, that a certain group of illaenids can properly be de- 
noted by this term, and the genus will be referred to later. 
THALEOPS Conrad, 1843. 
Proc. Acad. nat. sci. Phil., 1843, 1, p. 331. 
Type, THALEoPs ovata Conrad. 
The presence in this species of very high eyes on long peduncles, 
long narrow genal spines, deep dorsal furrows sharply delineating a 
prominent glabella, a narrow axial lobe, ten thoracic segments, and a 
small short pygidium, mark an unusually well-defined genus which 
seems to be confined to North America, and probably to the Ordovi- 
cian, though one Silurian species has been referred to the genus. 
Auceste Hawle and Corda, 1847. 
Prodr. monog. Bohm. tril., 1847, p. 66, pl. 4, f. 31. 
Type, ALCESTE LATISSIMA Hawle and Corda (which is the same as 
Illaenus hisingeri Barrande, according to Barrande). 
This genus is not valid, for it was based upon an immature speci- 
men showing only four segments, and was very incorrectly described 
and figured. Without Barrande’s explanation, no one would be able 
to identify the Alceste latissima with any Bohemian trilobite. 
Ruopore Angelin, 1854. 
Pal. Scandinavia, 1854, pt. 1, Trilobita, p. 38, pl. 22, f. 17. 
Type, RHoporE tinEata Angelin. 
The name Rhodope was used for a gastropod by von Siebold in 
1848 (Anatomie, p. 296), and Volborth replaced the name by Panderia. 
