442 ROBERT TRACY JACKSON ON ECHINI. 



This species is incompletely known, but I think it is clearly referable to the genus Pholido- 

 cidaris. Whidborne made the species the type of a new genus, Protocidaris. I see no need 

 of maintaining this genus, for the species as far as known fits well in the genus Pholidocidaris. 

 It certainly does not belong to the genus Echinocystis [Echinocystites] to which it is referred 

 by Messrs. Lambert and Thie'ry. 



Upper Devonian, East of Barnstaple, England, cotypes, Museum of Practical Geology 

 Collection 7,158, 7,159, and 16,358. The specimen no. 7,158 is the original of Whidborne's 

 Plate 25, fig. 1. Same locality, Oxford Museum (Sollas). 



Pholidocidaris gaudryi (Julien). 



Lepidoccntrus miinsterianus Julien, 1874, p. 76 (non de Koninck, 1869, p. 546, for which see Archacocidaris 



mucnsteriana, p. 280). 

 Melonites gaudryi Julien, 1890, p. 737. 

 Pholidocidaris gaudryi Julien, 1896, p. 131, Plate 16, figs. 1, 2, 6, 7; Lambert and Thiery, 1910, p. 123. 



This species is known only from fragmentary molds of plates and spines, and the descrip- 

 tion is gathered from Professor Julien's text and rather indistinct photographic figures. 



Ambulacra are arranged in six columns, limited on either side by adambulacral plates. 

 The ambulacral plates are hexagonal, 4 mm. wide, and about 1.5 mm. high, with pore-pairs 

 near the ventral border of each plate. They are ornamented on the exterior with a large, and 

 also small tubercles. The number of interambulacral columns is unknown, but a badly preserved 

 specimen led Julien to think that there are at least three columns in the neighborhood of the 

 apex. The interambulacral plates are irregular in form, and Julien says that they are similar in 

 form to those of P. irregularis. Two of the plates which he figures (his Plate 16, figs. 6, 7c) are 

 wide, high, rounded plates, with eccentric primary and secondary tubercles. These from their 

 shape and size are apparently plates from a right adambulacral column similar to what I show 

 in Plate 74, fig. 4. Julien says that the spines are of various sizes, expanded at the base, terete, 

 marked with fine longitudinal striae, and identical with those of Pholidocidaris irregularis. 



Lower Carboniferous, 1'Ardoisiere, central France. The types are in the possession of the 

 family of the late Professor Julien. 



MEEKECHINUS gen. nov. 



Test spheroidal, or flattened. The ambulacra are wide at the mid-zone, with in each 

 area numerous columns of small plates (twenty in the known species), and the interambulacra 

 are narrow, with in each area few columns of plates (three in the known species), all plates are 

 of about equal size. A small perforate primary tubercle with scrobicule and secondary tubercles 

 occur on ambulacral and interambulacral plates, also small primary and secondary spines on 



