(312 



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



There is no notch in the anterior margin. The posterior margin is high, and nearlj 

 vertical. The greatest width is at a third of the length of the test from the anterior 

 end. When seen from the side it appears high, and with tumid sides ; there is 

 a slight depression below the anus. The highest point is close to the posterior 

 margin ; thence there is a gentle slope forward to the steep, well-curved anterior 



Ambulacra : Petals broad, short, and but slightly depressed ; anterior ambulacrum 

 narrow ; the depression disappears where crossed by the fasciole. The anterolateral 

 ambulacra are broad, shallow, and blunt ; one and a half times as long as the postero- 

 lateral. These are curved backward beside the raised posterior interradius. 



Interradii : The posterolateral pair are wide near the apical system ; the corresponding 

 portions of the antero-lateral pair are sharp, and bear coarser tubercles than elsewhere. 



Fasciole wide, distinct, and fairly regular in its course. 



Apical system excentric posteriorly ; three genital pores ; ethmophract, madreporite 

 small and raised. 



Anus elongated, oval ; placed above a depression in the posterior margin. Anus just 

 visible from above. 



Mouth strongly bilabiate. 



Dimensions — 



Specimen from Citta Vecchia, 



Length, 

 Height, 

 Width at anterior third, 



,, posterior ,, 

 Maximum, 



Apical system : distance from anterior margin, 

 Mouth : distance from anterior margin, 

 Antero-lateral ambulacrum : length, 



„ „ width, . 



„ „ number of pores (post, zone), 16 



Postero-lateral : length, 



„ width, 



„ number of pores (anterior zone), 





Hemiaster scillcc, 





from Nodule Bed. 



16*5 mm. 



28 



mm. 



14 „ 



23 



>> 



16 „ 



25 



» 



H „ 



23-5 



?> 





27* 



)> 



9-5 „ 



13* 



»> 



4-5 „ 



9-5 



i) 



5 „ 



10* 



!> 



2-5 „ 



1 R 



4 



>> 



10 



3 mm. 



45* 



;> 



1-5 „ 



3 



>) 



>, &c). 



Citta. Vecchia — 



Nodule 



Distribution. — Malta — Globigerina Limestone (beds b, &c). 

 Seam No. 4, Fommer Reh. 



Remarks. — This pretty little species may be readily distinguished from Hemiaster 

 scillw, which also occurs in the nodule seams, by the fact that in the latter species the 

 apical system is slightly before the centre, the greatest width is across the same point, 

 and that the greatest height is at some distance from the posterior margin. The 

 measurements above quoted, especially those marked by an asterisk, bring out the 

 principal points of difference ; but in addition to these there is the greater depression of 

 the petals in H. scillce. 



