30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



Wright's (1856, pi. 22, fig. 2h) figure of the apical system in H. 

 caudaUis is incorrect. I have studied the same specimen under high 

 magnification and include (text fig. 6) a drawing of its apical system. 

 There are seven complementary plates instead of two, and oculars II 

 and IV are much larger than shown in Wright's figure. Mortensen 

 (1948, p. 115) also found large oculars in a specimen he collected 

 of this species. 



Family CLYPEIDAE Lambert, 1898 



Usually large, low, broad, with flat adoral surface; apical system 

 anterior, tetrabasal, always four genital pores ; periproct usually 

 longitudinal ; peristome anterior, pentagonal ; petals usually broad, 

 closed, of equal length, outer pores slitUke, strongly conjugate, all 

 ambulacral plates double pored ; bourrelets well developed ; phyllodes 

 in early species usually with three series of pore pairs in each half- 

 ambulacrum, in later, only one ; no buccal pores ; in later species 

 adoral tubercles larger than adapical, no naked granular zone in 

 interambulacrum 5. 



Genera. — Clypeus, Bothryopneustes, Pygitrus, Astrolampas, Psen- 

 dopyguriis. 



Range. — Jurassic (Bajocian) to Cretaceous (Cenomanian). 



Remarks. — The Clypeidae are most similar to the Nucleolitidae, 

 but differ in usually having a lower, broader, larger test, broader 

 petals with broad outer poriferous zones, and phyllodes with more 

 pore pairs. Pygurus and Pseudopygurus are distinct from any other 

 genera in the Nucleolitidae, but Astrolampas and Bothryopneustes 

 have characters intermediate between the Clypeidae and Nucleolitidae 

 and consequently blur the distinction between the two families. Astro- 

 lampas has the shape and wide petals of a clypeid, but the phyllodes 

 of a nucleolitid, and in Bothryopneustes the petals and phyllodes are 

 intermediate between those typical within the two families. Most of 

 the species of Clypeus have a wider, lower, and larger test, wider 

 petals with broader outer poriferous zones and longer, more crowded 

 phyllodes than in any nucleolitid, but there are a few species in which 

 these distinctive characters are not so well developed. 



Genus CLYPEUS Leske 



Clypeus Leske, 1778. Klein's Nat. dispos. ech., p. 93. Type species herein 



designated Clypeus plotii Leske. 

 Synonyms: Auloclypcus Pomel ; Crotoclypcus Pomel; Dactyloclypcus Mac- 



cagno; Echinoclypeus de Blainville. 



