292 ME. E. S. COBBOLD ON TRILOBITES [Aug. I9II,. 



Microdiscus. 



Microdiscus sp., cf. M. PUNCTATUs Salt. (PI. XXV, figs. 12 a-12c.) 

 J. W. Salter, Q. J. G. S. vol. xx (1864) p. 237 & pi. xiii, fig. 11. 



The specimen [1297] exhibits five or more imperfect internal 

 casts of a minute form of pygidium, about 1-| millimetres long, from 

 which I have compiled the outline sketches (PI. XXV, figs. 12 b 

 & 12 c). None of the specimens show the complete number of the 

 divisions of the axis, but I do not think that there could have been 

 more than seven or at most eight, including the articulating and 

 terminal portions. In this respect these pygidia differ from M.punc- 

 tatus Salter, and from the related forms M.scanicus and M. eucentrus 

 Linnarsson. 1 



Locality and horizon. — The upper section on the Shoot- 

 Rough Road, Comley ; from the Shoot-Rough-Road Flags, 1 or 2 

 feet below the ochreous band. 



Agraulos Corda. 



Agraulos (?) holocephalus Matthew. (PI. XXV, figs. 9 a-11 c.) 



G. F. Matthew, Trans. Eoy. Soc. Canada, vol. viii (1890-91) sect, iv, p. 138 & 

 pi. xi, figs. 5 a-o d. 



Dr. Matthew's species appears to be represented by several 

 cranidia, three of which [360-362] are figured. The last (PI. XXV, 

 fig. 9 a) has been much flattened by pressure, but the smallest 

 (fig. 11 a) seems to retain its original convexity, which is very high 

 (about 1 : 2.5). 



The most convex specimen shows no sign of any marginal rim ;. 

 but this feature is slightly marked in the other two specimens. 



Pigiditjm? (PL XXV, figs. 16a-16c). — Associated in the same 

 rock with these head-shields are two specimens of pygidia [376, 

 378] which may possibly belong to this species ; but, so far as 

 association goes, they might equally be referred to one or other of 

 the two species next to be noticed. 



Locality and horizon. — The upper section on the Shoot- 

 Rough Road, Comley ; from the ochreous band, about 4 feet below 

 the top of the Shoot-Rough-Road Flags. 



Agraulos sp., cf. A. quadrangtjlaris (Whitfield). (PI. XXV, 

 figs. 13, 14, & ? 15.) 



K. P. Whitfield, Bull. Amer. Mus. Nat. Hist. vol. i (1884-86) p. 147 & pi. xiv, 



fig. 8. 

 C. D. Walcott, U.S. Geol. Surv. Bull. No. 10 (1884) p. 48 & pi. vii, fig. 1. 



A second species, which is probably referable to Agraulos, is 

 indicated by specimens [369-371] from the same bed of rock as 



1 J. Gr. O. Linnarsson, ' De unci re Paradoxides Lagren vid Andrarum ' Sver. 

 Geol. Undersokn. ser. C, No. 54 (1883) pp. 29 & 30, pi. ii, figs. 17-20. 



