SYSTEMATIC DESCRIPTIONS CIDAROIDA. 21 



This species was based by Cotteau on a single specimen which con- 

 sists of an interambulacral area with a half-ambulacrum on either 

 side. The specimen measures 9.5 mm. in height. The width of the 

 interambulacrum at the mid-zone is 6 mm. and of each half -ambula- 

 crum 1.5 mm. As the width of an interambulacrum plus an ambula- 

 crum at the mid-zone equals 9 mm., the circumference of a complete 

 specimen of the same size would be about 45 mm. and the diameter 

 as estimated about 14 mm. The species is characterized by its low 

 and wide coronal plates and also by the fact that the areolse are so 

 small that their horizontal diameter is less than one-half the horizontal 

 width of the plate. On the other hand, in most West Indian cidarids, 

 the horizontal diameter of the areolse at the mid-zone is more than 

 half the width of the plate. Again, in clevei, the surface of the coronal 

 plates outside the areolae is rather uniformly tuberculated, and there 

 is a conspicuous scrobicular circle of secondary tubercles. Cotteau 

 says there are 7 to 8 interambulacral plates in a series (column) ; 

 7 were counted on the specimen; and a space for probably 1 additional 

 plate exists against the ambulacrum. There is no evidence, however, 

 for 9 plates in a column as shown in the right half of Cotteau's figure. 



Oligocene, Anguilla formation, from the island of Anguilla; holotype 

 and only known specimen, Guppy collection ex Cleve, U. S. Nat. Mus. 

 No. 115400. 



Cidaris melitensis Wright. 

 (Plate 1, Figures 12 to 17.) 







Cidaris melitensis Wright, 1855, Ann. Mag. Nat. Hist., ser. 2, vol. 15, p. 107, plate 4. figs, la toe. 

 Guppy, 1866, Quart. Jour. Geol. Soc. London, vol. 22, p. 299. Cotteau, 1875, 

 Kongl. Sven. Vet. Akad. Handl., vol. 13, No. 6, p. 8, plate 1, figs. 1 to 10. Guppy. 

 1882, Scient. Assoc. Trinidad, Proc., part 12, p. 194. 







The following is an extract from Cotteau's description of this 

 species: 



Species of medium size, circular, about equally depressed dorsally and 

 ventrally. Ambulacral areas relatively broad, a little depressed, sub- 

 undulate. Pores rounded, very open, disposed a little obliquely, each 

 pair of pores separated by a small elevation. Interporiferous areas very 

 narrow toward the poles, with 2 principal rows of granules near the pores 

 and with 2 vertical rows of smaller tubercles in each half-area at the ambitus. 

 Interambulacral tubercles prominent, strongly mammillate, perforate, 

 non-crenulate. Scrobicules large, subelliptical toward the peristome. 

 tending to become circular dorsally, bordered with a regular circle of small 

 mammillate granules. Beyond this circle the plates are rather sparingly 

 covered with small granules. Peristome subcircular, periproct subpen- 

 tagonal, and Cotteau says a little larger than the peristome. Spines elongate, 

 cylindrical, acuminate distally, furnished with granules disposed in longi- 

 tudinal series, more prominent toward the base. The upper end of the 

 spine appears to be quite smooth. 



In the U. S. National Museum there are 2 specimens of tests and 3 

 spines which are evidently the originals of Cotteau's figures. In 



