PHOLIDOCIDAIUS. 441 



width, and are of about equal height. The interambulacral plates bear a large eccentric per- 

 forate primary tubercle and secondary tubercles. They are quite similar in -i/e and oniainenta- 

 tion to those described by Tornquist. In addition, some relatively large ambulacra! plate- 

 occur. These are slightly wider than high; they measure about 8.3 to 11 mm. in width and 

 have a pore-pair nearly or quite in the center of the plates. With these large ambulacra! plates 

 are some that are very much smaller, which are probably dorsal plate-. In the larger plates 

 the pore-pairs are surrounded by a depressed ring, as is typical of the ventral ambulacral plates 

 in Pholidocidaris irregularis. On the reverse side of the slab are found a number of primary and 

 secondary spines. The primary spines are swollen at the base, terete, about 7.2 to 8.4 mm. in 

 length, and marked by very fine longitudinal striae. The secondary spines are much smaller, 

 about 2.8 mm. in length, and show no vertical striae. The number of columns of ambulacral 

 and interambulacral plates in an area is unknown, but from the large number of interambulacral 

 plates in the English specimen, which apparently represents a single individual, there are 

 probably a good many columns in an area. A large stout tooth, which, as far as preserved, 

 measures 28 mm. in length and is 9 mm. wide, bears evidence of a powerful lantern. 



Lower Carboniferous, Hunsriicken, Alsace, Germany; Coplaw, Clitheroe, Lancashire, 

 Museum of Practical Geology Collection 16,304. This is the first occurrence of Pholidocidaris 

 recorded from the Lower Carboniferous of Great Britain, but it occurs in the Devonian, as seen 

 from the next species described. 



* Pholidocidaris acuaria (AYhidborne). 

 Plate 74, fig. 11. 



Eocidaris (?) acuaria Whidborne, 1896, p. 376. 



Protocidaris acuaria Whidborne, 1898, p. 203, Plate 25, figs. 1-lb, 2, 2a; Klein, 1904, p. 7.">. 



Protocidaris [acuaria] Sollas, 1899, p. 709. 



Echinocystis acuaria Lambert and Thiery, 1910, p.' 118. 



This species is known only from external molds, which are confused iuues of plates and 

 spines. Judging from the molds, the interambulacral plates are large, from 4 to 5 mm. in 

 width, with an eccentric perforate primary tubercle and scrobicule and secondary tubercle-. 

 Whidborne says that the primary tubercle is central, but it is certainly not central in some 

 plates, and I have seen no proof that it is central in any plate*. 



There are impressions of a few large and also small ambulacral plates with a pair of pores 

 in each; in fact it is by the two small plugs representing casts of the pores that these plate- un- 

 recognized. The spines are primaries and secondaries; the primaries are swollen at the base, 

 otherwise about cylindrical, and the longest that I saw measured about ti mm. in length, but 

 they were not complete distally. The impressions of a stout lantern are plainly seen in one 

 of the specimens in the Jermyn St. Museum, no. 7,158. 





