160 Dr. J. W. Gregory — Egyptian Echinoidea. 



Length 37 mm. 



Breadth ... ... ... ... ... ... ... 35 mm. 



Ratio of breadth to length ... ... ... ... ... -9.5 



Height 27-5 mm. 



Eatio of height to length ... -74 



Apical disc : distance from anterior margin ... ... 17 mm. 



Apical disc : ratio of distance from anterior margin to length -46 



The specimen shows both peripetalous and lateral fascicles. The 

 dimensions show that the apical disc is anterior in position, and 

 hence the fossil is a Linthia. The echinid has, however, the very 

 short posterior ambulacral petals, while the petals of the anterior 

 pair are longer and more flexuous. The petals, moreover, are deep. 

 These characters are unusual in Linthin, but are very frequent in 

 ScJiizaster. Hence the species has more the characters of a Schizaster 

 with an anterior apical disc than of a normal Linthia. Cotteau, 

 indeed, I'emarks (op. cit., p. 243) that the French specimens have 

 the apical disc either central or even slightly posterior ; so that he 

 was doubtful as to the generic position of the species. 



The nearest allied echinid previously recorded from Egypt is the 

 Linthia Arizensis (D'Arch.), which is, however, much flatter and 

 more depressed. 



As there is only one specimen of this form, its specific determination 

 is necessarily somewhat uncertain. 



Genus SCHIZASTER, L. Agassiz, 1847. 



1. Schizaster Thebensis, De Loriol, 1881. 



Mem. See. Phys. Hist. nat. Geneve, vol. xxvii, p. 125, pi. ix, 



figs. 5-6. 

 Distribution. — Libyan Series: Todtenberg, near Assiut (De 

 Loriol-le-Fort) ; Coll. Geol. Surv. Egypt, ex No. 868. 



2. Schizaster Mokattamensis, De Loriol, 1883, 

 "Beitr. libysch. Wiiste," vol. ii, pt. 1, p. 41, pi. x, figs. 1, 2. 

 Distribution. — Mokattam Series : Mokattam (De Loriol-le- 

 Fort). Libyan Series : Gebel Ter, near Esneh (De Loriol-le-Fort) ; 

 Geol. Surv. Egypt, ex No. 867. 



3. Schizaster, Zitteli, De Loriol, 1881. 

 Mem. Soc. Phys. Hist. nat. Geneve, vol. xxvii, p. 122, pi. ix, fig. 2. 



There are one good and three crushed specimens of this species in 

 Nos. 864-5. 



Distribution. — Mokattam Series : Mokattam (De Loriol-le-Fort). 

 Libyan Series : Coll. Geol. Surv. Egypt, ex Nos. 864-5 ; Gebel Ter, 

 near Esneh (De Loriol-le-Fort). 



4. Schizaster Gaudryi, De Loriol, 1881. 



Mem. Soc. Phys. Hist. nat. Geneve, vol. xxvii, p. 120, pi. ix, fig. 1. 



Distribution. — Mokattam Series : near Tliebes ; Mokattam (De 

 Loriol-le-Fort). Libyan Series : Coll. Geol. Surv. Egypt, No. 996. 



The collection includes two specimens of this species. The two 

 specimens differ in the size of the anterior ambulacral depression; 



