REMOPLEURIDES NICHOLSON!. 



13 



slightly posteriorly, with a short median lanceolate pointed ridge reaching back 

 behind them to the notch in the pygidial margin between the inner pair of teeth. 

 Lateral lobes composed of two pairs of pleurae produced beyond margin to form 

 two pairs of teeth. First pleurae directed backwards forming sides of pygidium 

 with free points projecting beyond margin ; projecting knobs on front edge to fit 

 into sockets in last thoracic segment ; surface of pleurae marked by weak median 

 furrow. Second pleuras separated from first by faint inter-pleural furrow and 

 directed backwards to end in free but somewhat stouter teeth projecting behind 

 points of first pair and enclosing an angle of about 30°; no pleural furrow 

 present on surface. 



Surface of whole pygidium ornamented by minute tubercles and striations ; on 

 first pair of pleurse the striae are longitudinal, but on second pair are transverse 

 and sinuous, with the tubercles distributed irregularly between them. Doublure 

 of pygidium concentrically striated. 



Dimensions. — 



III. 



Length of glabella to base of tongue 

 ,, of ,, including tongue 



Width of „ between eyes . 

 ,, of tongue at base 



Length of free cheek . 



Width of ,, near 



edge of spine 



base to outer 



of base of cheek to subgenal notch 



IV. 



120 mm. 



17-5 „ 



17-0 „ 



7-0 „ 



13-0 „ 



9-7 „ 



6-8 „ 



12-0 „ 



6-0 „ 



6-0 „ 



7-75 „ 



7-50 „ 



4-20 „ 



II. 



ll'O mm. 

 16-0 „ 

 16-0 „ 



7-0 „ 



Width of thoracic axis at front end 



,, of „ at posterior end 



Length of anterior pleurae 

 V. Length of pygidium 

 Width of „ . 



,, of axis at front end 

 Bemarlcs. — This species was previously referred by me to B. colbii, Portlock, 

 as re-defined by Salter, but certain differences were at the same time pointed out, 

 though they were not regarded as of specific value. The characters of the free- 

 cheek and pygidium and the presence of the median spine on the ninth axial ring 

 of the thorax were at that time unknown, but with their discovery there is 

 sufficient reason to remove it from its previous specific association. Mrs. Gray has 

 now obtained some nearly perfect individuals from the Starfish Bed, so that we are 

 able to refer with certainty the detached or broken fragments hitherto only known. 

 The presence of the median spine on the thoracic axis and the characters of the 

 pygidium closely recall R. dorsospbdfer,^ but in the latter species there is no 

 1 Salter, 'Mem. Geol. Surv.,' dec. vii (1853), p. 4, pi. viii, figs. 3, 4. 



