GENERA AND GKOUPS OF THE ECHINOIDEA. 273 



Section Pyrmnodesonia. 

 (A subanal fasciole, others may be present.) 

 Greuus OvuLASTEE, Cotteau, 1884, Bull. Soc. Zool. de France, 

 vol. ix. p. 328. Semies, 1888, Bull. Soc. Geol. Fr. ser. 3, 

 vol. xvi. p. 803. 



Test of moderate size, thick, elongate, rounded and sliglitly 

 enlarged in front, sub-acuminated and truncated bebind, sligbtly 

 keeled above and tumid actinally, very faintly grooved in front. 



Apex very excentric in front. Apical system witb the four 

 lateral basal plates in contact, the madreporite in the right an- 

 terior plate. 



Ambulacra dissimilar, flush with the test and apetalous ; the 

 anterior narrow, and its pores less apparent than those of the 

 others. Antero-lateral ambulacra very widely divergent, with the 

 poriferous zones arched concavity forwards. All the paired am- 

 bulacra are narrow, barely flexuous and very angular at the apex ; 

 poriferous zones composed of small pores lodged in fossettes, 

 arranged in close pairs near the apex and much more distant 

 towards the peristome. The pores open quite at the base of the 

 plates, which are tall. 



Tubercles abundant, scrobiculate, the intermediate granules 

 homogeneous. The peristome is subcircular, slightly sunken, and 

 very excentric in front ; the sternum long and sub-pointed. The 

 periproct is oval, high up, and is near the summit of the posterior 

 surface. A subanal fasciole. 



Fossil. Cretaceous : Europe (France). 



Grenus Pal^oteopus, Loven, 1872, Etudes, p. 17, pis. xii., xiii., 

 & xxxii. A. Agassiz, 1881, Report on Challenger ' Echini, 

 p. 157; 1883, Beport on ^ BlaTce' Echini, p. 54, pi. xviii. 

 Loven, 1883, Pourtalesia, p. 78, fig. 208. 

 The test is small, has an ovoid contour, is uniformly tumid 

 above, moderately convex below, and is slightly flattened poste- 

 riorly, and well rounded at the sides, smooth. 



The apical system is slightly excentric in front, consolidated, 

 and more or less pentagonal. The basal plates are fused in a mass, 

 and there are no sutures ; the madreporite is indicated by a fissure, 

 or by pores near the position of the right anterior plate. The 

 radial plates are distinct, small, and perforated, and the posterior 

 pair are separated. There are but two generative ducts having 

 their pores at the tops of two large tubular eminences. 



LINN. JOUEN.— ZOOLOGY, VOL. XXIII. 18 



