24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



Remarks. — The Galeropygidae are distinguished from the Nucleo- 

 litidae by having subpetaloid ambulacra instead of the well-developed 

 and often broad petals found in the Nucleolitidae. 



This family concept coincides with Lambert and Thiery's (1921, 

 P- 336), but not with Mortensen's (1948, p. loi), whose use of the 

 family is far broader. He includes the genera LorioleUa, Desorella, 

 Galeroclypeus, Infraclypeus, and Menopygus, but all these genera 

 lack phyllodes and usually petals and should not be referred to any 

 family in the Cassiduloida. 



Genus GALEROPYGUS Cotteau 



Galeropygus Cotteau, 1856. Bull. Soc. Geol. France, ser. 2, vol. 13, p. 648. Type 



species by original designation, Hyboclypus agariciformis Wright. 

 Synonym : Ressopygits Pomel. 



GENERIC DESCRIPTION 



Medium to large size, low or domed, circular ; apical system tetra- 

 basal, genital plates forming semicircle around adapical border of 

 periproct ; petals slightly developed, narrow, all ambulacral plates 

 double pored ; periproct in contact with apical system, longitudinal, 

 groove leading from opening to posterior margin ; peristome anterior ; 

 bourrelets slightly developed ; phyllodes double pored with many pore 

 pairs arranged in three series ; no buccal pores ; tubercles perforate, 

 crenulate, not arranged in vertical series, slightly larger on adoral 

 surface. 



Comparison with other genera. — Galeropygus is very similar to 

 Hyboclypus, having slightly developed petals, its periproct in contact 

 with the apical system, and similar phyllodes with numerous pore 

 pairs arranged in three series in each half-ambulacrum. It differs 

 in having a broad apical system with the genital plates arranged in 

 a semicircle, whereas in Hyboclypus the system is elongate with 

 genital plates 2 and 3 usually separated from plates i and 4 by ocular 

 plates II and IV. Furthermore, in Galeropygus the bourrelets are 

 slightly developed, but are absent in Hyboclypus. 



Range and distribution. — Jurassic (Toarcian to Oxfordian) of 

 Europe. 



DESCRIPTION OF TYPE SPECIES 



GALEROPYGUS AGARICIFORMIS (Wright) 

 Plate I, figures 1-4; text figure 2 



Hyboclyptis agariciformis Wright, 1851. Ann. Mag. Nat. Hist., ser. 2, vol. 9, 

 p. 99- 



