SEA-uncnixs. 447 



Order HOLECTYPOIDA. 

 Fanuly I. PYGASTERID^. 



Subfamily 1 . P y G A s t E R i N ^.. 

 (Jenus Pyoaster Agassiz. 



Subgenus 1. Pygaster sens. str. 



,, 2. Ilegapj/gus, nom. nov, 

 „ 3. Alacropygns Cotteau, 



Subfamily 2. P i L E i N ^. 



Genus 1. PiLEUS Desor. 



,, 2. Anorthopygus Cotteau, 



Family II. DISCOIDIIDyE. 



Subfamily 1. Holectypinj5. 



Genus 1. Holectypus Desor. 



Subgenus 1. Holectyjnis Desor. 



,, 2. Caenholectypus Pomel. 

 „ 3. Lanieria Duncan. 



Genus 2. Coptodiscus Cotteau &, Gautliier, 



Subfamily 2. D i s c o I d 1 1 N .E. 

 Genus Discoidea Agassix. 



Family III. CONULID^. 



Genus Conulus Leske. 

 lucertje sedis : — Discholectypus Pomel. 



Order HOLECTYPOIDA Duncan (emend.). 



Euecliinoidea Irregularia Avith external peristomial branchiae 

 (Ectobranchiata) and a central moutb armed with jaws and 

 surrounded by a perignathic girdle (Gnathostomata). 



Ambitus circular, subpentagonal, posteriorly truncated, or 

 slightly elongated. Adapical surface acutely or bluntly conical, 

 apex practically central. Peristome central, usually circular, some- 

 times decagonal or even obliquely elliptical in outline. Perigna- 

 thic girdle discontinuous, composed of both processes and ridges. 

 Jaws more like those of the Regularia than of the Clypeastroida. 

 Periproct very variable in size and position, always posterior. 



