7 Echinoid Tests, Cidaroida. 99 
crenélées, pores unigeminés, bordés de granules égaux et réguliers», he mentioned 
several species in stratigraphical order, but designated no genotype. Lampert (1900) 
considered that the genus was allied to Eotiaris, differing only in the more complete 
rigidity of the test (p. 40); apparently he placed it in his tribe Rhabdocidarinae (p. 
53); he referred to it (p. 44) some ten species, none of which occurred in Pome ’s 
list. From among these may here be mentioned the Rhaetic species P. Curionii, 
P. Cornaliae, and P. Ombonii (all of Stoppani), and P. senex Lampert. Subsequently 
(1902), in referring Cidaris Blumenbachi Mbnst. to Paracidaris Pomer, LAMBERT 
made Paracidaris a subgenus of Plegiocidaris. 
The diagnosis given above is slightly condensed from that drawn up by 
Savin (1903), who maintained Plegiocidaris as a subgenus of Cidaris, distinct from 
Paracidaris, and definitely selected as genotype Echinus coronatus Scuiors., which 
was one of the species mentioned by PoMEL 
DeLace and Herovarp (1904) speak of Plegiocidaris, Paracidaris, and Pro- 
cidaris, as allied but independent genera. 
Although Pomet included in Plegiocidaris species from Trias to Tertiary, no 
subsequent author has mentioned any species below Rhaetic or above Jurassic. It is 
probable that the «<2 a 3 triasiques» of PomMEL were species now referred to 
Miocidaris. The essential difference between the two genera lies in the nature of 
the sutures, and this, as we have seen, was a character that changed quite gradually. 
The Plegiocidaris—Procidaris series is, however, further distinguished by the increas- 
ing size of the ambulacral tubercles, which tend towards the formation of compound 
ambulacrals. Without the evidence of ambulacrals it is perhaps unsafe to refer to 
this genus an isolated interambulacral plate, especially from a Cassian horizon. But 
the existence of the genus at that time is not impossible. 
Plegiocidaris? sp. indet. 
(Plate VIII. figs. 188., 189.). 
Material. — One interambulacral plate from the Cassian Beds of Cserhat, 
Leitnerhof. 
Description of Specimen. — The margins of the plate being broken, its 
outer measurements are uncertain. The main tubercle has a depressed hemispheroidal, 
perforate mamelon, with a transverse diameter of 1.15 mm. and a vertical diameter 
of 1.2 mm.; its slightly undercut neck rests on a platform of circa 15 mm. diameter, 
with about 20 small, rather obscure crenellae. From this the boss slopes, with 
almost straight, slightly concave sides, to the edge of the scrobicule, which is cir- 
cular and very slightly sunk, with a diameter of 2.7 mm. There is a scrobicular 
ring of 20 secondary tubercles, apparently imperforate. The extra-scrobicular surface 
bears only a few smaller isolated tubercles. 
Relations of the Specimen. — As indicated above, it is hard to say 
whether this belongs to Miocidaris or Plegiocidaris. So far as specific characters 
go, it is sufficiently distinguished from all described species of Miocidaris by the 
sparse extra-scrobicular tuberculation. There is no trace of bevelling or denticulation 
of any of the margins, such as would cause one to refer it to Miocidaris; but 
this might be due to the imperfection of the specimen. The ornament, however, 
reminds me of some species of Plegiocidaris, and it may be noted that a circular 
scrobicule occupies almost the whole of the plate in P. Curionit. 
7* 
