278 Annals of the South African Museum. 



Ambulacra petaloid, prominent, nearly closed. The pefcaloid part 

 of the anterior ambulacrum reaches to within a short distance of the 

 anterior margin ; pores somewhat oblique, those of the inner row 

 rounded, and connected by a groove with the pores of the outer row 

 which are slightly elongate. Poriferous zones wide. Interporiferous 

 zone elevated, slightly broader than the poriferous zones, and bearing 

 small scrobiculate tubercles. 



Antero-lateral ambulacra with the petaloid parts broader and 

 shorter than in the anterior ambulacrum, and with the interporiferous 

 zone relatively wider. Anterior poriferous zone with more oblique 

 pores and a rather greater curvature than in the posterior zone. 

 Pores and tubercles similar to those of the anterior ambulacrum. 

 Posterolateral ambulacra with the petaloid parts rather narrower 

 than in the antero-lateral ambulacra, and reaching to about two- 

 thirds of the distance from the apical disc to the margin. 



Interambulacra slightly raised between the jjetaloid parts of the 

 ambulacra, with numerous small scrobiculate tubercles on the upper 

 surface of the test. On the base of the test the tubercles are larger 

 and more deeply sunk. The median raised band possesses rather 

 less coarse and more irregular ornamentation than the rest of 

 the base. 



Peristome pentagonal, a little in front of the centre of the base, 

 with a distinct fioscelle and prominent bourrelets. Periproct ovate, 

 in a short furrow, on the upper part of the sub-truncate end. 



Affinities. — Cassidulus umhonatus differs from the type species of 

 Cassidulus in having a concave instead of a fiat base, and in the 

 ambulacra being more distinctly petaloid. In the form of the base 

 it resembles some species found in the Senonian of Algeria and 

 Tunis, which are .referred by Cotteau, Peron, and Gauthier='- to the 

 genus Echinohrissus, e.g., E. sitifensis, Coquand; E. suhsitifensis, 

 Peron and Gauthier ; E. pyramidalis, Peron and Gauthier. 



These species were placed by Pomel f in his genus Trochalia, and 

 were also regarded as distinct from both Cassidulus and Echinohrissus 



* Echin. Foss. de I'Algeiie, vol. ii., fascic. 8 (1883), pii. 161, 162, 164. Gauthier, 

 Echin. Foss. de la Tunisie (1889), pp. 46, 47. 

 t Genera des Echinides (1883), p. 60. 



