MR J. W. GREGORY ON THE MALTESE FOSSIL ECHINOIDEA. 



615 



Professor Laube has clearly indicated* the differences between Pericosmus altus and 

 his P. affinis, from the Leithakalk. 



Species 2. Pericosmus COranguinum, n. sp. Plate II. figs. 3 and 4a, b. 

 Synonymy — 



Hemiaster gratelowpi, T. Wright (non Sism.), 1855, "Foss. Echinod. Malta," Ann. Mag. Nat. Hist. 



(2), xv. pp. 189, 190. 

 Brissopsis „ T. Wright (non Sism.), 1864, " Foss. Echinidse Malta," Quart. Journ. Geol. 



Soc, xx. p. 484. 



Diagnosis. — Form — Species large, as wide as long, nearly circular, anterior margin 

 not indented by the anterior furrow, or very slightly so. Sides tumid. Seen from the 

 side, the posterior margin is vertical, and from the summit of this the posterior inter- 

 radius rises very slightly to the highest point just behind the apical disc. From this 

 point the anterior slope is somewhat steep to the well-rounded anterior margin. There 

 are a couple of prominent areas in the lower posterior margin, separated by a broad but 

 shallow depression which runs up to the anus. 



Ambulacra : Paired petals long, deeply impressed, and subequal in length. The 

 anterior ambulacrum is shallow, and disappears at or is continued only as a very slight 

 depression below the fasciole. The antero-lateral petals are strongly divergent ; at the 

 lower ends they curve forward slightly. The posterior pair are a little shorter than the 

 others, and curve back towards the ridge of the posterior interradius. 



Apical System central ; four genital pores ; ethmolysian ; the posterior part of the 

 madreporite greatly expanded. 



Fascioles : The peripetalous is well marked, but the lateral indistinct. 



Anus oval ; high on the vertical posterior margin. 



Mouth bilabiate ; very near to the anterior margin. 



Dimensions — 





Type 





Type 





Specimen. 





Specimen 



Length, . . 



50f mm. 



Mouth, distance from anterior margin, 



9 mm. 



Width, .... 



60t „ 



Antero-lateral ambulacrum, length, . 



23 „ 



Height, .... 



36 „ 



,, „ width, . 



4 „ 



,, of posterior margin, 



33 „ 



Postero-lateral ambulacrum, length, . 



18 „ 



Apical system, distance from anterior 





„ „ width, . 



4-5 „ 



margin, 



29 „ 







Type.— Brit. Mus., E. 3405. 



Distribution. — Malta — Globigerina Limestone. 



* " Ech. osterr.-ung. ob. Tertiarabl." Abh. k. k. geol. Reichs., v. 1871, p. 68, pi. xvii. f. 2. 



t The length has been reduced by crushing; a specimen that better retains its shape gives a length of 62 mm. and 

 a width of 60 mm. 



