48 PROS'. P M. DUKCAN's BEYISIOlir OF THE 



Genus Aceosalenia, Agassie, 1840, Ech. foss. de la Suisse, pt. 2, 

 p. 38. Duncan ^ Sladen, 1887, Ann. Sf Mag. Nat. Hist. 

 ser. 5, vol. xix. p. 128. 



Test moderate in size, depressed, tumid at tlie circular and 

 rarely pentagonal ambitus, rounded above, flatter actinally. 



Apical system ratber large, four anterior basals large, and tbe 

 posterior smallest and diiFering in sbape. A dorso-central plate 

 in tbe antero-posterior axis of tbe system, in contact witb tbe four 

 larger basals and anterior to tbe periproct. Supplementary plates 

 to tbe dorso-central may occur. Posterior radial plates enter 

 tbe ring of tbe periproct, rarely a radial separating tbe antero- 

 lateral and postero-lateral basals. Periproct large and posterior. 



Ambulacra narrow, witb primary plates near tbe apical system 

 and witb compound plates near tbe ambitus and actinally. Com- 

 pound plates of united primaries witb rare demi-plates, except 

 near tbe peristome. Pairs crowded and biserial near tbe peristome, 

 from tbe presence of demi-plates. Tubercles of tbe interradia 

 largest, perforate and crenulate ; tbose of tbe ambulacra mucb 

 smaller, or only as large granules. 



Peristome large, decagonal, witb well-developed brancbial 

 grooves witb raised edges. Perignatbic girdle witb low ridges 

 and slender processes sometimes uniting. Spines large and small, 

 tbe former striated longitudinally, or plain, and often not quite 

 circular in transverse section ; smaller spines striated. 



Fossil. Lias and Oolites: England and Europe. Lower Creta- 

 ceous: N. Africa. 



II. Family Hemicidaeid^, WrigIif,lS57,Fal. Soe., EcTi. 

 Ool. Form. p. 68. {Amended.) 



E-egular ectobrancbiate gnatbostomes witb tbe test tbick, more 

 or less spberoidal, depressed or tall or subcorneal. Ambulacra 

 increasing in widtb actinally ; primary tubercles well developed, 

 but smaller tban tbose of tbe interradia, extending or not tbrougb- 

 out in two vertical rows ; pairs of pores in ares actinally wbere 

 tbe plates are compound. Interradia large, plates few ; tubercles 

 very large at tbe ambitus, variously sized actinally and dorsally, 

 and may be obsolete tbere. Scrobicules often coalescing. Peri- 

 stome decagonal, ambulacral lips large, brancbial incisions well 

 developed. Perignatbic girdle witb interradial ridges and united 



