SYSTEMATIC DESCRIPTIONS CLYPEASTRINA. 43 



where it is not rare ; also in the vicinity of Havana, Cuba, where it is 

 rare, collection of Comisi6n del Mapa Geol6gico de Espana. Lambert 

 reports a single badly preserved specimen from Antigua, which from 

 its association with Clypeaster lanceolatus and Echinolampas lycopersicus 

 he attributes to the "Miocene" [Oligocene], collected by J. W. Gregory 

 in 1899, collection British Museum. 



Clypeaster duchassaingi Michelin. 



Clypeaster duchassaingi Michelin, 1861, Mem. Soc. Geol. de France, ser. 2, vol. 7. p. 107, plate 

 9, figs, a to g. 



Test convex, sloping upwards from its thick margin, differs from C. 

 rosaceus and ellipticus by its flat base and petals not swollen. 



Michelin gives as "formations madreporiques," Guadeloupe, Antilles. 



Clypeaster ambigenus (Lamarck). 



Scutdla ambigena Lamarck, 1816, Anim. sans Vert., vol. 3, p. 12. 



Clypeaster ambigenus Blainville, 1834, Manuel d'Actinolgie, p. 216. Michelin, 1861, Mem. 

 Soc. Geol. de France, ser. 2, vol. 7, p. 113, plate 15, figs, la to /. 



The following is a description of this species : 



Test low, rounded, flattened on base. Differs from rosaceus by its flat- 

 tened base and large tubercles around the peristome. 



Michelin says: "formations modernes et madreporiques," Guade- 

 loupe. He says it also occurs in the "Eocene" of Jacksonboro, Georgia. 



Clypeaster placentoides, new species. 

 (Plate 7, Figures 1, 2.) 



The following is a description of this species: 



This species is represented by 2 individuals, a larger and a smaller, the 

 latter resting on the dorsal face of the larger, as shown in the figures. The 

 test is ovally rounded, a little longer than wide, thin, biscuit-like in shape, 

 being very much flattened dorsally. The margin is relatively thin and the 

 ventral side as far as shown on the larger specimen is very flat. The apical 

 disk is central in position, but no details of structure are preserved. Ambu- 

 lacral petals are nearly flush with the surface, rounded and moderately 

 open at the distal ends. Poriferous areas sunken, the inner and outer rows 

 of pores curved in outline. Furrows connecting the pores are moderately 

 deep, with 3 or 4 tubercles on the intermediate ridges. Tubercles are 

 small dorsally, larger and more densely associated on the ventral side. 

 Periproct round, very near the posterior border of the test, as shown well 

 on the larger specimen. 



The larger specimen (on which the smaller rests, as seen in Plate 7, 

 figs. 1, 2) measures 75 mm. in length, 65 mm. in width, and about 

 14 mm. in height. The periproct is only 1.5 mm. from the posterior 

 border of the test. This larger specimen shows something of the flat- 

 ness of the lower side and tubercles on the same, but does not show the 

 peristome or ambulacral furrows which are hidden by the matrix. The 

 smaller specimen measures 54 mm. in length, 48 mm. in width, and 



