Vol. 52.] SILURIAN SPECIES OF ACIDASPIS. 237 



second species under the name of A. coronata. This, and not 

 A. Brighti, is the Paradoccides quadrimucronatus of Murchison. 



Beyrich's Odontopleura Brightii is a different species, and is 

 identical with Acidaspis quinquespinosa, Salter MS. 



Actdaspis coronata, Salter. (PI. YII. fig. 6.) 



1839. ? Paradoxides quadrimucronatus, Murch. ' Sil. Syst.' p. 658, pi. xiv. fig. 10. 



1845. ? Odontopleura mutica, Emmrich, Neues Jahrb. 1845, p. 44 ; 1846. Beyrich, 

 'Unters. ub. Tril.' p. 19, pi. iii. fig. 5. 



1848. Acidaspis Brightii (pars), Salter, Mem. Geol. Surv. vol. ii. pt. i. p. 348, 

 pi. ix. figs. 8, 9 (not figs. 6, 7). 



1853. Acidaspis coronatus, Salter, Mem. Geol. Surv. dec. vii. pi. vi. p. 7; 1854. 

 Morris, ' Catalogue of Brit. Fossils,' 2nd ed. p. 99. 



1854. Acidaspis Marklini, Angelin, ' Pal. Scand.' p. 38, pi. xxii. fig. 13. 

 1854. Acidaspis multicuspis, Angelin, ' Pal. Scand.' p. 37, pi. xxii. fig. 12. 

 1857. Acidaspis coronata, Salter, Quart. Journ. Geol. Soc. vol. xiii. p. 210., 

 1885. Acidaspis Marklini, Lindstrom, Ofv. kongl. Vet.-Akad. Forh. Arg. 42, 



no. 6, p. 54, pi. xiii. figs. 8, 15, pi. xvi. fig. 10. 



1888. Acidaspis mutica, Wigand, Zeitschr. deutsch. geol. Gesellsch. vol. xl. p. 93, 

 pi. x. figs. 19, 20. 



General form broadly ovate, depressed. 



Head large, semilunar, the angles drawn out into broad spines ; 

 granulate. Glabella triangular; median portion nearly parallel- 

 sided ; the basal lateral lobe is considerably larger than the second ; 

 both are rounded and well-defined, but confluent on the inner side 

 with the median portion of the glabella ; anterior lateral lobes 

 obsolete. Frontal border nearly straight, smooth, projecting beyond 

 the margin of the free cheeks. The facial suture in front of the eye 

 is nearly parallel to the axis, behind the eye is continued almost at 

 right angles, and cuts the posterior margin not far from the genal 

 angle. Eyes small, prominent, placed far back, close to the occipital 

 furrow ; ocular ridge curved. Eree cheeks easily separable, granular, 

 steeply inclined, bearing at the margin a row of about twelve short 

 spines ; produced at the genal angles into broad spines, the borders 

 of which are nearly continuous in direction with the borders of the 

 cheeks. 



The thorax consists of ten segments. Axis narrow. Pleurae 

 straight, at right angles to the axis ; produced into spines, which are 

 strongly bent backwards. Each pleura bears a prominent ridge, on 

 which is a row of small tubercles, sometimes indistinct. The spines 

 also are granulate. 



Tail broad, short. The axis consists of two segments. Erom the 

 anterior ring a strong rib proceeds on each side to the margin, 

 where it is produced and forms a primary spine. There are four 

 secondary spines between the two primaries, and one outside each. 

 All the spines are directed straight backward, and they are gene- 

 rally short. The margin, spines, and other prominent parts bear 

 tubercles, and there is generally one somewhat larger than the 

 average, at the base of each spine. 



Horizons and Localities. — Wenlock Limestone : Dudley ; Walsall ; 

 Malvern; Pen-y-llau, Cardiff. Lower Ludlow: Vinnal Hill, Ludlow.; 

 Dudley. A very much crushed specimen in the Museum of Practical 



