Jurassic Fauna from Central Arabia. 399 
such a form as Pygurus costatus, Wright, from British 
Corallian rocks. Iam obliged to Dr. F. A. Bather, F.R.S., 
for suggesting the reference of this specimen to the genus 
Pygurus, which is characteristic of Jurassic seas, although 
occurring as well in Cretaceous times. 
Locality. Bachain. 
Rhabdocidaris sp. (Pl. XI. fig. 13.) 
This determination, kindly confirmed by Dr. F. A. Bather, 
refers to a well-preserved fragmentary spine belonging to 
Desor’s Rhabdocidaris—a genus which is particularly charac- 
teristic of Upper Jurassic deposits, although recognized also 
from older Cretaceous rocks. This spine is of trilateral form 
and bears a central longitudinal ridge on one of its faces, 
whilst the other surface is much depressed but furnished also 
with a median ridge of a more rudimentary type. The lateral 
margins are equidistantly spined, the ridge-summit is 
tubercled, while the remainder of the surface is covered with 
closely set, longitudinal, microscopical striations composed 
of minute beaded tubercles of varying dimensions. The 
specimen appears to be related to R. orbignyana, Agassiz * 
from the Kimeridgian of Europe (Nattheim, &c.). 
Locality. Bachain. 
ACTINOZOA (Corals). 
Montlivaltia sp. 
A small and simple turbinate coral, possessing a rounded 
calyx full of closely arranged radial septa; the central struc- 
ture of the cup is obscured by a hard matrix. Numerous 
dissepiments are observable between the septa in the calycular 
region as well as longitudinally, where the epithecal covering 
has been partially dissolved away during fossilization, thus 
exposing the septal ‘Structure. In places the epitheca is 
coated with “ Beekite.” Montlivaltia is a well-known 
Jurassic genus, although the specimen requires more study 
and should also be sectioned before its relationships are 
ascertainable with described species. At present the specimen 
is suggestive of an Upper Jurassic age, between the 
Sequanian and Kimeridgian. 
* See Desor, ‘Synopsis des Echinides Fossiles,’ 1858, p. 40, pl. viii. 
figs. 7-9. 
