110 Dr. T. Wright on Fossil Echinoderms 



intervening spaces, so that the surface of this Echinus has a 

 very tuberculated appearance. The poriferous avenues are on a 

 level with the test ; the pores are arranged in triple oblique 

 pairs ; between each pair there is a slight elevated ridge ; every 

 two ridges of each triple oblique pair of holes is connected by 

 another ridge, which runs at an angle of 45° to them ; by this 

 arrangement the poriferous avenues exhibit a curious zigzag 

 character through these little elevations of the test in the line 

 of the pedal pores. The base is flattened, the mouth-opening 

 is large and decagonal, and the jaws and teeth are narrow and 

 much curved inwards ; the apical disc is absent in all the speci- 

 mens we have examined ; the space for the same is, however, of 

 moderate size. 



Affinities and differences. — This species may be distinguished 

 from Echinus Sen'esii, Desmoul,, fi'om the Molasse de Provence, 

 in having larger tubercles, with less granulation at their base, 

 and the absence of the zigzag ridges between the pairs of pores : 

 from Echinus dubius, Agass., another tertiary species from the 

 Molasse of Villeneuve in Provence, it is distinguished by the 

 more uniform size of its tubercles, the depression of the upper 

 surface, and the zigzag ridges of the poriferous zones. 



Locality and stratigraphical range. — It was collected from bed 

 No. 1, the Gozo marble, Malta, where it is not uncommon. We 

 have dedicated this species to the Earl Ducie, who collected the 

 beautiful specimens we have figured. 



Family Clypeastrid^. 



This natural family includes all the Urchins which have a 

 circular, elliptical, or pentagonal form, with a thick test, the 

 surface of which is closely covered with small, nearly equal- 

 sized tubercles sunken in the plates, and surrounded by ring- 

 like areolas ; these all carry short hair-like spines. The mouth 

 is large, central and pentagonal, and is armed with five strong 

 jaws which carry the same number of teeth : the anus is pos- 

 terior, and marginal or inframarginal : the interior of the test 

 is sometimes divided by pillar-like processes of the inner layer 

 of the plates. The dorsal portions of the ambulacral areas have 

 a petaloid form, circumscribed by large poriferous zones ; the 

 basal portions are narrow, rectilineal, or branched. The five 

 genital plates form a circle around the madreporiform body, 

 and between these are wedged the five ocular plates. This 

 family includes the genera Clypeaster, Lamk., Laganum, Klein, 

 Echinarachnius, Van Phels., Arachnoides, Klein, Scutella, Lamk., 

 Dendraster, Agass., Lohophora, Agass., Encope, Agass., Rotula, 

 Klein, Mellita, Klein, i?Mwa, Agass., Moulinsia, Agass., Scutellina, 



