SYSTEMATIC DESCRIPTIONS CLYPEASTRINA. 41 



flushness and the shallowness of the pore-pair furrows. Petals open at 

 the tips. Apical disk in the center of the test. The peristome doubtless 

 is central in position, but is not visible. Tubercles are well preserved, 

 rather scattered dorsally, closely associated ventrally. Periproct small, 

 situated on the ventral side, 3 mm. from the posterior border of the test. 

 The holotype measures 21 mm. in height, 68 mm. in length, and 58 mm. 

 in width in the plane of ambulacra II and IV, which is the widest part 

 of the test. The petals of ambulacra II, III, and IV give closely the same 

 measurements, namely, 21 mm. long by 12 mm. wide at the widest part; 

 petal I is in part hidden, but petal V, the left posterior, measures 27 mm. 

 in length by 13 mm. in width. 



This species is readily distinguished by its flattened, biscuit-like 

 form and the almost invisible character of the petals. 



Oligocene, Antigua formation, Rifle Butts, Antigua, T. W. Vaughan 

 collector, February 1914, 3 specimens, all very well preserved, U. S. 

 Geol. Sur. station 6854; the holotype, U. S. Nat. Mus. No. 328239, 

 and 2 paratypes, U. S. Nat. Mus. No. 328240. Base and western slope 

 of Friar's Hill, Antigua, T. W. Vaughan collector, February 1914, 1 

 specimen, much worn, U. S. Geol. Sur. station 6856. The stratigraphic 

 position of the horizon at which these specimens were collected is near 

 the bottom of the Antigua formation. 



Clypeaster cotteaui Egozcue. 



(Plate 6, Figures 6 to 8.) 



Clypeaster cotteaui Egozcue in Cotteau, 1897, Bol. Com. Mapa Geol. Espafia, vol. 22, p. 40, 

 plate 10, figs. 1 to 4. Lambert, 1915, Mem. Soc. d'Agric. de l'Aube (Troyes), vol. 

 79, p. 24. 



The following is an extract from the original description of this species : 



Test of moderate size, oval, a little narrowed anteriorly, upper surface 

 slightly convex. Margin thick and rounded. Lower surface concave, 

 with ambulacral furrows which expand and deepen as they approach the 

 mouth. Peristome pentagonal. Periproct circular, slightly separated from 

 the margin. Apex nearly central, very little excentric anteriorly. Apical 

 disk small, with madreporite constituting a relatively large star. Ambulacral 

 areas superficial, petals truncate and very open at the distal tips. Poriferous 

 areas a little depressed and very characteristic, the inner series of pores 

 curving and converging near the apex of each ambulacrum, below which 

 they make a nearly straight line to the distal tips, but converging. The 

 outer series of pores curve throughout their whole length, forming in the 

 extreme tip a curve of less radius, converging to meet the inner series; as 

 a sort of termination, 4 pores, smaller and elongated, form an irregular 

 quadrilateral. Each poriferous plate has 6 tubercles. 



The specimen figured measures 20 mm. in height, 65 mm. in length, 

 and 52 mm. in width in the line of ambulacra II and IV. The ambula- 

 cral petals I, V, and III measure 22 mm. in length and ambulacral 

 petals II and IV measure somewhat less, 18 mm. in length. Petals I 

 and V measure 14 mm. in width, but petals II, III, and IV are some- 

 what narrower, measuring only 12 mm. in width. The periproct is 3 

 mm. from the posterior border of the test. 



