70 F. B. Cowper Reed — On Phacojis Weavevi, Salter. 



Salter at this time admitted that his knowledge of this species -was 

 but slight, and though he believed that all the specimens which he 

 figui'ed belonged to one species, yet expressly stated that he " would 

 prefer to keep the name for the fossil of the May Hill Sandstone". 

 Moreover, as the specimens from the doubtful Ludlow rocks of 

 Horse-shoe Farm, figured in his monograph on pi. iii, figs. 2, 3, were 

 attributed by him to a "larger form of the species ", it is clear that 

 Salter's intention was to regard the specimens from Long's Quarry 

 (of May Hill Sandstone age) as the typical form. Accordingly, it is 

 on the characters of these latter that the species must rest. 



The pygidium is figured in the decade ii, pi. i, fig. 16, somewhat 

 incorrectly and diagrammatically as above mentioned, but only one 

 (No. 19221) of the three specimens in Jermyn Street seems to have; 

 been used in the much more accurate figure given in his monograph, 

 pi. iv, fig. 7. The head-shields from the same horizon were illustrated 

 by two figures in the monograph on pi. iii, fig. 1, and pi. iv, fig. 6. 



Of the three examples of the pygidium two are internal casts 

 (Nos. 19221, 19222) and the other (No. 19220) an external 

 impression. The shape of these pygidia is parabolic ; the length of 

 the type (No. 19221) is about 11 mm. (but the posterior margin is 

 rather imperfect) and its width 14-15 mm. ; the length of its axis 

 is about 10 mm. and its width at its front end 5 mm., audit tapers 

 regularly at about 20°-25° to its bluntly pointed exti-emity. Though 

 the posterior margin is not clearly preserved in this specimen, so 

 that its mucronate or non-mucronate character cannot be decided, 

 yet in the external impression (No. 19220) from Long's Quany, 

 and especially in another specimen in the Wyatt-Edgell Collection 

 from Tortworth in precisely the same rock, it is found to be not 

 acutely pointed nor mucronate, but obtuse and rounded, as indeed 

 Salter rightly shows in his figure (pi. iv, fig. 7). With regard to 

 the axis in specimen No. 19221, only the anterior two-thirds or 

 three-fourths are distinctly annul ated, being composed of 8 complete 

 rings, but the posterior part (which is, however, somewhat abi'aded) 

 shows 5-6 faint incomplete rings. In the external impression 

 (No. 19220) 14-15 rings can be counted on the axis, but the last 

 3 or 4 are indistinct. The total number of axial rings, therefore, 

 is 13-15. 



The lateral lobes are gently convex, as Salter mentions, but possess 

 only eight ribs. Salter's figure (Mon., pi. iv, fig. 7) shows only this 

 number in spite of the greater number given in the description. 

 These ribs are gently and regularly curved, and successively decrease 

 posteriorly in length and strength, the last pair being very short and 

 nearly parallel. All the ribs seem marked with a very faint, fine, 

 submedian line for about three-fourths of their length, and this feature 

 is especiall)^ well seen in the external impressions. In the internal 

 casts the ribs are separated by interspaces (interpleural furrows) as 

 wide as the ribs themselves, but in the external impressions it is 

 seen that these interpleural furrows are really quite narrow. The 

 ribs and furrows end abruptly against the border, which is smooth 

 and narrow, but definite ; and in the best preserved examples it is 

 clear that it does not appreciably widen behind and that it is not 



