from the Island of Malta. 107 



Junior. Autero-posterior diameter 2 inches, transverse dia- 

 meter 1-^j inch, height l-fp inch. 



Description. We have identified this Urchin with that figured 

 by Parkinson in his ' Organic Remains/ not however without 

 much hesitation, inasmuch as that figure is without details, and 

 is moreover drawn from a distorted specimen. We have in vain 

 endeavoured to find out the original, and have therefore, from 

 the central position of the apical disc and the great divergence 

 of the ambulacra, and from its being at the same time the most 

 common of all the Maltese Schizasters, and the one most likely 

 to have been sent to Parkinson, adopted Defrance's identifi- 

 cation. The test is heart-shaped, its widest part being at a 

 line drawn across the disc ; from this imaginary line the back 

 slopes obliquely forwards, and the border is rather bevelled away 

 at the cheeks ; from the same line backwards there rises a pro- 

 minent ridge which bends over into a short tail-like process. The 

 ambulacral areas (3 a) are deeply sunken, the single ambulacrum 

 has a tapering lanceolate form, and the anteal sulcus is deep and 

 narrow ; the poriferous zones lie in the angle of the depression ; 

 they consist of twenty-five pairs of holes, of which the outer 

 series is the largest ; the length of the petaloidal portion of this 

 area from the apex to the fasciole is 1^ inch. The antero- 

 lateral ambulacra (3 a) are more divergent in this species than 

 in the other Schizasters met with in the same rocks; they are 

 Ig^ inch in length and are slightly curved outwards and back- 

 wards ; they make an angle of 35 ; the number of pores (3 c) 

 in the zones is respectively thirty-six and thirty-four, the apical 

 eight pairs being almost microscopic: the postero-lateral pair 

 are y^ths of an inch in length and slightly /-shaped; they are 

 directed backwards at an angle of 65, and are proportionately 

 narrower than the anterior pair ; there are twenty-two pairs of 

 holes in each of the zones, the upper six pairs of which are 

 microscopic. The peripetal fasciole (3 b) is distinctly defined and 

 passes close to the bases of the petaloid portions of the ambu- 

 lacra, but at a short distance from the sides thereof it describes 

 a curve inwards in passing over the anterior interainbulacra, and 

 dips obliquely into the anteal sulcus where it unites with that of 

 the opposite side. The lateral fasciole is large and very distinct ; 

 it takes a backward and downward course towards the base of 

 the posterior border, and joins its fellow at some distance be- 

 low the anus ; the two fascioles form the letter V in their trajet 

 on the test. The apical disc is situated very near the centre of 

 the back, removed a little nearer to the posterior than the ante- 

 rior border ; it is perforated with four equal-sized genital holes. 

 The anus is oblong, situated high up in the obliquely truncated 

 posterior border, in which is a triangular depression limited on 



