262 PRor. p. M. DTiNCAiir's revision of the 



peristomial plate ; the plates 2 and 3 of zone " a " of the right 

 posterior interradium united ; an amphisternum. 



Periproct, high up in the posterior face, elliptical, vertical, with 

 well-developed plates, largest at the edge. Tubercles largest 

 actinally, with short delicate, often spatufete spines, smaller and 

 crowded abactinally with shorter and silky spines. 



"Fascicles, an internal, an anal not closing above, and a closed 

 subanal, including three ambulacral pores on either side, belong- 

 ing to 7ih to 9th plates, with penicillate tentacles. 



J'o^szY. Eocene: ? Europe. Miocene : Europe. Late Tertiary: 

 England, N. America. 



Mecent. N. British and Scottish seas, IS., Atlantic, Mediter- 

 ranean, Japan, E. Indian seas, E. Africa, Cape of Good Hope, 

 Australian and N. Zealand seas, Elorida, N. & S. Carolina, Brazil. 

 Littoral to 2675 fms. 



Genus Beetnia, Desor, 1847, Ann. So. Nat. Zool. ser. 3, 

 vol. viii. p. 12. Gray, 1855, Cat. JRec. Ech. Brit. Mus. pt. i. 

 p. 45. A. Agassiz, 1872-4, Revision, p. 578. Loven, 1874, 

 Etudes, pi. 41 ; 1883, PourtaIesia,-p. 55. Duncan 4" Sladen, 

 1885, Pal. Ind. ser. xiv., Foss. Eel. W. Sind, p. 842, pi. Iv. 



Test moderate and large, thick, ovoid or cordiform in tumid 

 marginal outline, depressed, flatly arched dorsally, highest behind 

 tlie centre, rounded and notched in front, obliquely truncated 

 behind, actinally resting on a spot anterior to the peristome, and 

 on the posterior point of the small triangular plastron. 



Apical system in front of the vertex, small, with four basal 

 plates ; the madreporite separating the basal plates, and ex- 

 tending posteriorly and separating the posterior radial plates. 



Anterior ambulacrum in a more or less decided groove, which 

 notches the anterior part of the test, the single pores numerous 

 dorsally ; tentacles long, slender, truncated, and wdth small pro- 

 cesses ; and beyond the crossing of the inner fascicle, anteriorly, 

 the pores are larger and more distant. Lateral ambulacra trian- 

 gular beyond the internal fascicle, with few small single pores 

 converging to the apical system, within its area ; the outer series 

 of pores in pairs large and separated by costae. The antero- 

 lateral ambulacra nearly transverse, the postero-lateral straight 

 or wavy and not very distant distally ; pairs of pores as in the 

 antero-lateral ambulacra. Actinally the posterior ambulacra 

 have wide zones which limit the plastron. 



