﻿22 ME. E. 8. COBBOLD ON TRILOBITES FROM [Feb. I91O,. 



Axial furrow.— Xarro wand sharply impressed on the exterior,, 

 wider on the internal cast. 



Side -lobe. — Evenly convex; curving down from the axial 

 furrows; confluent round the tip of tho axis, where also it fre- 

 quently overhangs the marginal rim ; it has one well-marked groove 

 close to the anterior border, which is a little raised at its edge. 



Marginal rim. — Xarrow all round, and bent downwards rather 

 more decidedly than in the head-shield. 



Test. — Relatively to other trilobites from the same rock, thick 

 and firm and resistant to weathering : marked by numerous im- 

 pressed punctse set at fairly even distances and represented on the 

 interior by raised spots, which are reproduced as punctso on the 

 internal cast. 



The variations are very slight, chiefly consisting in the amount 

 of inflation of the swollen parts. 



This species appears to be somewhat intermediate between 

 M. speciosus, Ford, and M. punctatus, Salter: with both it agrees 

 in having a punctate test, and a simple form of pygidium ; but, 

 whereas the present species has about seven annulations of the axis,. 

 M. punctatus is described as having nine, and M. speciosus eleven. 



The enlarged occipital ring, coalescent with the glabella, may be 

 paralleled in M. punctatus, but is not produced in the form of a 

 spine. From both these species it differs in having a plain marginal 

 rim to the head, and in the proportionate length of the glabella. 



In the plain marginal rim and punctate test it may be paralleled 

 with M. lenaicus, von Toll ! ; but it differs from that species, in 

 having a longer glabella and more convex axis to both cephalon' 

 and pygidium. 



Locality and horizon. — The grey limestone of Comley, from 

 the uppermost band (3 inches thick) at the excavation 200 yards 

 south of the quarry. 



MlCRODISCTJS lobattjs (Hall). (PI. Ill, figs. 17 & IS.) 



J. Hall, ' Pal. N. York ' vol. i (1847) p. 258 & pi. Ixvii. figs. 5«-5 f. 



C. I). Walcott, U.S. Geol. Surv. Bull. 30 (1*80) 1>- 156 & pi. xvi, figs. 1, la, 



1 b ; and 10th Ann. Rep. U.S. Geol. Surv. 1888-89 1 1800) p. 032 & pi. lxxxi,. 



figs. 1, 4tf, 1 b. 

 P. Lake. ' British Cambrian Trilobites' Monogr. Palaeont. Soc. vol. lxi (1907) 



pt. ii, p. 32 & pi. iii, figs. 4-6. 



Head-shields of this species from the same locality and bed as 

 M. comleyensis, sp. nov.. have been figured by Mr. Philip Lake in 

 his monograph. Since that portion of his work was published,, 

 several pygidia referable to M. lobatus have been found, one of 

 which [445], together with a very well-preserved head-shield [453], 

 is figured on PI. III. 



Locality and horizon. — Comley, from the uppermost band, 

 of grey limestone, and from the next lower band, at the excavation 

 200 yards south of the quarry. It is plentiful there. 



1 ' Beitr. z. Kenntn. d. Sibirischen Canibrium " Mem. Acad. Imp. Sci. 

 St. Petersb. ser. 8, vol. viii, no. 10 (1898) p. 23 & pi. i, figs. G-8, 10, 11, 

 14-17, 24. 



