262 PROCEEDINGS OF THE 



PerUremite does not appear to be nearly allied to any hitherto recog- 

 nised British form, and is probably an imdescribed species. 



Similarly formed radial plates occur in P. obesus (Lyon)* with 

 ornamentation of a like character, but certain other features of the 

 calyx do not correspond 



Locality and Horizon. — Kidlaw Quarry, near Gifford, Hadding- 

 tonshire, from shale above the No. 2 limestone, Lower Carb. lime- 

 stone group. Collection of the Geological Survey of Scotland. 

 Collected by Mr. James Bennie. 



In pursuance of this subject, it may not be out of place to give 

 an illustration of the ambulacra originally found by Mr. Bennie, 

 and which in all probability is one of those of the above species. 



In form elongately petaloid, tapering towards the outer ex- 

 tremity, traversed by a median flexuous ambulacral furrow (PI. V., 

 fig. 8). The component plates are not distinguishable, being 

 apparently all anchylosed together, but the sides of the lancet 

 plate bounding the ambulacral furrow are on each side crenulated. 

 The groove in the ambulacral furrow gives off short alternate, 

 equidistant, lateral branches on each side, which communicate 

 with depressions in the pore plates close against their crenulated 

 margins, which in no way perforated the plates, and are, therefore, 

 of the nature of sockets,* and not pores. From the true pores 

 (PL V., figs. 96-126) along the external margins of the pore plates 

 run in other and somewhat longer grooves, which terminate in 

 similar but larger sockets to those just described, and set alter- 

 nately with them (PL V., fig. 8b). 



The under surface of the ambulacrum is flattened (PL V., figs. 9, 

 11, and 12), the lateral portions showing the divisions of the plates 

 running from the pores (PL V., figs. 11 and 12). The central 

 part, which, is marked by four longitudinal ridges (Fig. 9c), repre- 

 sents the lancet plate of the larger Pentremites. In cross section 

 the respective parts just described are clearly distinguishable : 

 the central furrow, the arched pore plates on each side terminating 

 laterally in flange-like projecting margins, and the flat base. 



The small slits or nicks in the margins of the ambulacra (PL 

 V., figs. 96-126) probably represent the pores as previously de- 

 scribed, but no separation into pore plates and supplementary pore 

 plates is visible, the whole being apparently anchylosed together, 

 and the sutures obliterated. 



*D. D. Owen's Third Kentucky Report, Atlas, t. 11, f. \b. 



