150 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I44 



Clarkiella Lambert, 1916a. Rev. crit. palaeozoologie, vol. 20, p. 169. Type 

 species by subsequent designation Lambert and Thiery (1921, p. 369), Cassidu- 

 lus conoideus Clark {in Clark and Twitchell, \gis)=iCassidiiliis hemisphericus 

 Slocum, 1909, Lambert (1920b, p. 138) proposed a substitute name, Cossman- 

 naster, for Clarkiella, thinking the latter to be a junior homonym of Clarkella 

 Walcott, 1908, a brachiopod. The two names, however, are not spelled the 

 same, and Clarkiella is not a junior homonym. 



DESCRIPTION OF TYPE SPECIES 



HARDOUINIA HEMISPHERICA (Slocum) 



Plate 21, figures 6-10 



Cassidiiliis hemisphericus Slocum, 1909. Field Mus. Nat. Hist., Gcol. scr., vol. 4, 

 No. I, p. 7, pi. I, figs. 7-9. 



Material. — Holotype and a figured specimen studied. 



Shape. — Medium size, circular in marginal outline, highly inflated, 

 almost as high as long; sides vertical, adoral surface flat; sutures 

 depressed. 



Apical system. — Anterior, tetrabasal. 



Ambulacra. — Petals well developed, broad, closing distally, of equal 

 length, extending almost to margin ; interporiferous zones wide, twice 

 width of poriferous zones ; poriferous zones broad, slightly depressed, 

 pores conjugate, outer pore elongated transversely, slitlike; inner 

 round. 



Periproct. — Marginal, low on vertical posterior margin, small, 

 longitudinally elongated. 



Peristome. — Anterior, shape not known. 



Floscelle. — Bourrelets strongly developed, probably pointed and 

 toothlike ; phyllodes single pored, broad, pores arranged in two series 

 in each hal f -ambulacrum ; approximately eight pores in each outer 

 series, two in each inner series; buccal pores present. 



Occurrence. — Upper Cretaceous (Late Maestrichtian) of south- 

 eastern United States. 



Location of type specimen. — Chicago Museum of Natural History, 

 P. 10347. 



Remarks. — All authors have considered Clarkiella as a separate 

 genus, although Cooke (1953, p. 18) suggested that it might prove 

 to be either a synonym or subgenus of Hardoidnia. Mortensen sep- 

 arated it because of what he considered to be its distinctive apical 

 system. However, its apical system is very similar to that found in 

 the type species of Hardoiiinia, H. mortonis, and it has no genital 5 

 as suggested by Mortensen. 



