NO. 3 CASSIDULOID ECIIINOIDS — KIER 147 



lodes (chart 7, fig. d) are even wider, and shorter, with fewer pores 

 in the inner series ; and the first pore of the inner series is more 

 distant from the peristome than in the earher H. bassleri. In the 

 Lower Maestrichtian species, H. mortonis (MicheHn) and H. por~ 

 rectus (Clark), the phyllodes (chart 7, figs, e, f) are much shorter 

 and wider and the inner series more reduced with only one to three 

 pores in each series. In the lower-middle Maestrichtian species H. 

 meglameryae Cooke, H. kellumi (Stephenson) and H. aequorea (Mor- 

 ton), the phyllodes (chart 7, figs, g-i) are similar, but in the latest 

 known species, H. emmonsi (Stephenson), the inner series (chart 7, 

 fig. j) is practically absent and the phyllodal pores are arranged in an 

 arc. 



There appears to be an evolutionary trend in the structure of the 

 apical system. In the Santonian species H. bassleri (text fig. 119) the 

 madreporite is much smaller and the other genital plates larger than in 

 the later species such as H. potosiensis (text fig. 120), H. mortonis 

 (text fig. 121), H. porrectus (text fig. 122), and H. kellumi (text 

 fig. 123). Unfortunately, the apical system is not visible in the oldest 

 species, the Turonian H. stantoni. It is probable that there is a trend 

 with an increase in the size of the madreporite and a decrease in the 

 other genital plates, but the apical system must be seen on all the species 

 in order to confirm this trend. 



Remarks. — Weisbord's Clypeopygus hahanensis is herein referred 

 to Hardouinia (see p. 70 for discussion). 



Range and distribution.— \J-ppev Cretaceous (Turonian to Mae- 

 strichtian) of the United States, Mexico, and Cuba. 



DESCRIPTION OF TYPE SPECIES 



HARDOUINIA MORTONIS (Michelin) 



Plate 21, figures 1-4; text figures 121, 124; chart 7, figure e 



Pygorhynchus mortonis MicheHn, 1850. Rev. Mag. Zool., ser. 2, vol. 2, p. 240. 



Material. — Seventy-five specimens studied in the U. S. National 

 Museum. 



Shape. — Medium to large, average specimen 50 to 55 mm. long ; 

 circular in outline except for pointed posterior ; highly inflated ; ad- 

 orally depressed or flat. 



Apical system. — Slightly anterior, tetrabasal, (text fig. 121) sutures 

 difficult to see ; madreporite very large, posteriorly extending between 

 ocular plates V and I, other genital plates very small. 



Ambulacra. — Petals very well developed, broad, equal length, clos- 



