216 Professor H. L. Hawkins — 



related to apical system as in PlesiecMnus. Ambulacra exceedingly 

 narrow, homogeneous, built (? exclusively) of small, low primaries 

 bearing small, approximately similar granules. Pore-pairs minute, 

 homogeneous and uniserial ? throughout. Interambulacra pro- 

 portionately very broad ; built of low, bent plates each bearing a 

 single scrobiculate, ? perforate, primary tubercle near the adradial 

 margin, and sundry scrobiculate granules scattered irregularly among 

 the abundant fine granulation. Primary tubercles never large, but 

 notably reduced on the adapical surface, Radioles, etc., unknown. 



PsEUDOPYGASTER Gen. nov. 

 (Genotype : P. eos, Middle Lias.) 

 Pseudopygasteridse with the characters of the family. 



PsEUDOPYGASTER EOS sp. nOV. (PI. IX, figS. 1-6.) 



(Holotype : Brit. Mus., No. E, 16505, Lower part of Middle Lias, 



Kelat Valley, Persia. Paratype : Brit. Mus., No. E, 16506, same 



horizon and locality.) 



Measurements in millimetres. 



Ant. post, diameter ..... 40-8 = 1 



Max. Transv. diameter .... 42-5 = 1-04 



Height c. 22-5 = 0-55 



Apical system (axis 2 — V) . . ? 25-0 = 0-61 



Peristome c. 3-4 = 0-08 



Periproct (greatest width visible) . . 7-2 



Interambulacrum (width on ambitus) . . 22-0 = 1 



Ambulacrum (width on ambitus) . . 2-0 = 0-09 



Plates in interambulacral column on adoral 



surface .....? 7 



No. of amb. plates to one iamb, (on 



ambitus) . . . . , c. 10 



The ambital outline (Figs. 1, 2) is subpentagonal, with the 

 angles equally truncated. The angles of the resulting decagon 

 coincide with the main interradial tubercle-series. The posterior 

 interambulacral margin is strongly concave. The ambitus is very 

 tumid (Fig. 3) ; the adapical surface is roughly hemispherical, the 

 adoral surface almost flat. The apical system is invisible, save 

 possibly for the distal angle of the madreporic genital and the site 

 of ocular V as determined by the tapering of the ambulacnim 

 (see Fig. 1) ; it must tave been proportionately large, and vtill 

 have been centred on a point well behind the adapical pole. The 

 peristome (Fig. 2) is almost exactly midway between the anterior 

 and posterior margins ; but, making allowance for the concavity of 

 interradius 5, is very slightly in front of the centre. Its margin 

 is apparently circular, with doubtful traces (in negative) of very 

 feeble branchial incisions, but no indication whatever of perignathio 



