
66 RECORDS OF THE S.A. MUSEUM 
EEY TO SPECIES. 
Keys are neeessarily arbitrary. In that dealing with the species of Cyclaspis, 
and presented herein, an attempt has been made to eroup as far as possible forms 
with broad structural features in common. Its use will necessitate a more than 
cursory examination of material in hand, but that is really necessary whatever 
form of summary is adopted. 
Following the inevitable addition of forms as yet unknown and with fuller 
knowledge of some of those already recorded, there is no doubt that modification of 
the key will be necessary. 
STRUCTURE. 
Carapace. The primary surface pattern consists of the universal fine net- 
work (fig. 9, C; 32, D, ete.), offen linked with faint pitting but always present 
even in the most polished forms. This minute reticulation may follow the forma- 
tion of ridges in that the edves are placed end to end along the line of a carina, as 
in the only one occurring in pingwis, that of the dorsum, which runs the whole 
length of the animal (fig. 30, F). The relative size of the reticulation shows some 
specific variation. 
postero-laicral tubercle transverse ridge 2 
~ 



median dorsal t bercle 
transverse ridge b. 
antero-lateral “ee 
tubercle 1 rl 
an, c 
° 
<3 ~~ 
a i 
antero-lateral 
tubercle 2 

———" 
Pig. 2. Ridges and tubercles of carapaew of Cyclaspis tribulis juvenile. 
Superimposed, as it were, on the fine network, there may be a much larger 
secondary reticulation formed by a denser calcification of ihe edges of rather 
deep pits. This produces the honeyeomb-like effect referred to by Zimmer in 
deseribing: bicornis (1921a, p. 127, fie, 22); it is well-marked in some members of 
the exseulpta group and is illustr ated herein for mawsonae (fig. 40). The edees 
of the secondary reticulation may be placed end to end so as to play a part in 
emphasizing true carinae (mawsonae) or pseudo-earinae (hicornis). 
The ridge most commonly present is that running alone the mid-dorsal line; 
it is very rarely absent, but may be faint, particularly on the posterior half. Along. 
side the anterior half of it there is often a more or less distinet shallow depression 
