306 F. E. Coicper Reed — Undescrihed Trilohites. 



falcate instead of long spinose ends distingiush them. Moreover, 

 the characters of the pygidium and head- shield completely separate 

 0. Planti from the subgenus Paraholina. 



The only other British forms calling for any comparison are the 

 so-called ' Conocoryphe^ Williamsoni (Belt)/ the species of Para- 

 holinella described by Miss Crosfield and Miss Skeat,- and Olenus 

 triarthrus (Callaway) from the Shineton Shales. Belt's species 

 probably belongs to Pai-abolinella, the only important point of 

 difference being the presence of two instead of three pairs of 

 glabellar furrows. The pygidium of ' Conocoryphe ' Williamsoni 

 seems to be almost identical with that of 0. Planti, and the 

 pleuree are very similar, but the characters of the glabella and 

 head-shield are sufficient to warrant their specific separation. 



The species of Parabolinella from the Tremadoc of Nant y 

 Glasdwr, described by Miss Crosfield and Miss Skeat (loc. cit.), is 

 only known by an imperfect head-shield. It difiers from 0. Planti 

 by the greater number of glabellar furrows, by the larger eyes, by 

 the course of the facial sutures, and by the narrower fixed cheeks. 



The only other British species of Parabolinella is P. [^Olenus^ 

 triarthrus (Callaway),^ from the Shineton Shales, and it diff'ers from 

 P. Planti by its broader glabella, by the union of the posterior and 

 anterior pairs of glabellar furrows, by the tubercles on the axial 

 rings of the thorax, and by the characters of the pygidium. But it 

 is evidently a closely allied species. 



Olenus (Ctenopyge?) expansus, Salter. (PI. XII, Figs. 2 and 3.) 



1873. Olenus {Sphcerophthalmtis) expansus, n.sp., Salter : Cat. Camb. Silur. Foss. 



Woodw. Mus., p. 12 (« 275). 

 1877. Olenus {SphcBTophthalmus) expansus, Woodward: Cat. Brit. Foss. Crust., p. 47. 

 1891. Olenus {Sphcerophthalnms) expansus, "Woods : Cat. Type Foss. Woodw. Mus., 



p. 149. 



The two specimens on which Salter founded this species are 

 exceedingly imperfect and fragmentary, and consist only of a few 

 broken thoracic rings attached in one case to a portion of a pygidium 

 showing the margin. This specimen, though crushed and flattened 

 out, is the less incomplete of the two, but is extremely unsatisfactory 

 for a specific description. Salter (loc. cit. supi-a) describes the species 

 thus : " A very narrow axis and enormously wide flanks distinguish 

 this." The long narrow pleurae, of which 7-8 are visible in the 

 better and larger specimen and 7 in the smaller one, are straight, 

 with parallel sides, extend at right angles to the axis, and bend 

 sharply close to the ends to terminate in short points, not projectirig 

 outwards nor produced into spines. Each pleura is apparently 

 furnished with a narrow raised rounded ridge running along its 

 Ulterior margin, with a distinct groove behind it. The general 



1 Geol. Mag., Dec. I, Vol. V (1868), p. 5, PI. II, Figs. 7-11. Salter's Cono- 

 coryphe Williamsoni (Cat. Camb. Sil. Foss. Woodw. Mus., p. 12) is distinct from 

 Belt's form. 



2 Q.J.G.S., Tol. lii (1896), p. 537, pi. xxvi, figs. 11 and 12. 



3 Callaway : Q.J.G.S., vol. xxxiii (1877), p. 666, pi. xxiv, fig. 6. Brogger : 

 Nyt Magazin filr Naturvidenskaberne, vol. xxsvi (1897), pp. 178-185, 200. 



