F. R. Cowper Reed—Fauna of the Bokkeveld Beds. 167 
(a) Trilobita. 
The trilobites include the following species, adopting Schwarz’s 
(2, pp. 382-460) modifications of Lake’s (3) list :— 
Homalonotus agrestis, Schwarz. Ph. (Cr.) callitris, Schwarz. 
ZT, colossus, Lake. Ph. (Cr.) Ceres, Schwarz. 
H. Herscheli, Murchison. Ph. cristagaili (Woodward). 
HI. hippocampus, Schwarz. Ph. (Cr.) Gydowi, Schwarz. 
HH. horridus, Schwarz. Ph. impressus, Lake. 
HI. lex, Schwarz. Ph. oceilus, Lake. 
H. perarmatus, Frech. Ph. pupillus, Lake. 
H. quernus, Lake. Phacops ? sp., Lake. 
H. Herscheli, var. or sp. noy., Schwarz. Dalmanites lunatus, Lake. 
HT. sp., Lake. D. sp., Lake. 
Phacops acacia, Schwarz. Proetus malacus, Lake (? = Pr. Ricardi, 
Ph. ( Acaste ?) africanus, Salter. Schenck). 
Ph. arbuteus, Lake. Typhloniscus Baini, Salter. 
Ph. (Crypheus) caffer, Salter. 
By the foregoing list it will be observed that out of the 26 species 
of trilobites so far recorded, 22 (or 24 if we include Dalmanites in the 
genus Phacops) belong either to the genus Homalonotus or Phacops, 
using the latter name in a broad sense. The distinction of the.various 
species and their precise number is a matter of some uncertainty, some 
of them having been founded on isolated pygidia and others on isolated 
head-shields, which in some cases at any rate probably belong to the 
same species. ‘There is also a difference of opinion as to the specific 
union of some of the types, Schwarz splitting up Salter and Lake’s 
H. Herschel into four species, and ascribing Lake’s type of Ph. erista- 
galli to a new species, Ph. acacia. 
In the above list the subgeneric names and references of certain of 
the Phacopide are given according to Schwarz and Lake’s usage. 
But it may be pointed out that neither of the terms Acaste nor 
Crypheus can be applied to trilobites for reasons of priority (4) (5). 
With regard to the rightful inclusion of any of the South African 
species in either of the two groups or subgenera signified by these 
names, Salter, Lake, and Schwarz have generally been doubtful, 
though Lake (3, p. 211) says that Ph. caffer is a ‘‘ true Crypheus.” 
The group designated by the name Crypheus (Green, 1837) was 
founded on the American species Cr. Boothi, Green, in which the 
axis of the pygidium has 10-14 rings and the lateral lobes 5 ribs 
produced into spines round the margin, and there is also a more or 
less developed median terminal spine in the variety Cr. collitelus, 
Green. Hall & Clarke (6, p. xxxii) defined the subgenus Crypheus 
(genus Dalmanites) as follows: ‘‘Genal angles produced into long, 
often laterally compressed, and narrow spines. Posterior thoracic 
segments produced and acute. Pygidium with five annulations and 
five pairs of marginal lobes or spines. ‘Terminal lobe more or less 
developed.” Ph. caffer has 10-11 rings on the axis of the pygidium 
and 5 ribs on each lateral lobe produced into spines. Ph. ocellus and 
Ph. impressus ave probably also allied, though the pygidial axis in the 
former bears only 7 rings and in thelatter only 8-9. In Cr. Barrist, 
Hall, of the Hamilton Group there are only 6-8 rings on the axis, so 
that the small number in these two species is not quite exceptional. 
