SYSTEMATIC DESCRIPTIONS CLYPEASTRINA. 47 



pores, whereas Peronella has only 4 genital pores, the pore being 

 absent in area 5. 



Laganum elongatum Egozcue. 



Laganum elongatum Egozcue, in Cotteau, 1897, Bol. Com. Mapa Geol. Espana, vol. 22, 

 p. 26, plate 4, figs. 1 to 4. 



I have not seen a specimen of Laganum elongatum. It is a relatively 

 large species; Cotteau says 16 mm. in height, 74 mm. in length, and 

 55 mm. in width. It is flat, but high and rounded on the borders. 

 Ventrally it is flat near the border, but deeply hollowed around the 

 peristome. The ambulacral petals are narrow, acuminately pointed, 

 with narrow poriferous areas. The apical disk is not known in the 

 species, but it is assumed that it had 5 genital pores. If 4 only existed, 

 then it would be referred to Peronella instead of Laganum. 



Cotteau refers the single specimen described to the "Miocene," from 

 the environs of Matanzas/ Cuba, collection of Comision del Mapa 

 Geologico de Espana, Madrid. 



Genus PERONELLA Gray, 1855. 



Type species. Laganum peronii Agassiz, 1841, Monographies 

 d'Echinodermes, Scutelles, p. 123. 



The genus Peronella as well as Laganum among Recent species is an 

 Indo-Pacific type in its distribution. It is therefore very interesting 

 to find the genus represented fossil in the West Indies. It may be 

 pointed out that of the 6 species referred to Laganum in Clark and 

 Twitchell's memoir (1915, Mon. U. S. Geol. Sur., vol. 54), each is 

 described as having 4 genital pores and might therefore be properly 

 referred to Peronella rather than Laganum. 



Peronella mirabilis, new species. 

 (Plate 9, Figure 3.) 



The following is a description of this species : 



Test small, thin, elongate, subpentagonal in outline, dorsally slightly 

 elevated, with rounded low margin, flat ventrally. Ambulacral petals 

 are narrow, pointed, but open slightly at the tips. Petals I, V, and III 

 are of the same length, 6 mm.; petals II and IV are a little shorter, 5 mm. 

 in length. Poriferous areas are narrow and curved; interporiferous areas 

 lanceolate, about half as wide again as a poriferous area. Apical disk 

 anterior, 8 mm. from the anterior border and 9.5 mm. from the posterior 

 border of the test. Peristome and periproct are invisible, as they are 

 covered up by matrix on the ventral side. The most remarkable feature 

 of this species is the tubercles; dorsally there are 6 large, perforate primary 

 tubercles, sunken in deep pits, the upper part of the tubercles being flush 

 with the surface of the test; 2 of these large sunken tubercules are situated 

 in interambulacrum 1 and there are also 2 in interambulacrum 4. In the 

 anterior interambulacra 2 and 3 there is in each area one of these large 

 tubercles, a most distinctive and, as far as I know, unique character in 

 the Clypeastroida. 1 Secondary tubercles of medium size are scattered over 



1 What at first sight looks like a second tubercle in interambulacrum 3, and lying close to the 

 petal of ambulacrum III, is a local imperfection and not a tubercle. 



