262 Dr. T. Wright un Fussil Echinoderms 



XXIV. — On Fossil Echinoderms from the Island of Malta ; icith 

 Notes on the stratigraphical distribution of the Fossil Organisms 

 in the Maltese bed^. By Thomas Wright, M.D. &c., Professor 

 of the Natural Sciences in the Cheltenham Grammar School. 



[Conclucled from p. 196.] 



Genus Schizaster (Agassiz, 1834). 



Urchins with a cordiforrn test, broad and depressed before, 

 nari'ow and elevated behind; the ambulacral summit excentral 

 and nearer the posterior border ; the petaloid ambulacra lodged 

 in very deep depressions, the antero-lateral much longer than 

 the postero-lateral pair; the single ambulacrum long and deeply 

 sunken in the anteal sulcus ; the peripetal fasciole surrounds 

 the ambulacral star, and from one of the antero-lateral angles 

 thereof, a second postero-lateral fasciole arises, which passes 

 downwards and backwards along the sides and under the anus, 

 where it joins its fellow of the opposite side ; the genital pores 

 are two in number from the fusion of the anterior and posterior 

 pairs ; the five ocular plates are small and lodged in depressions ; 

 the eye-holes are microscopic. Schizaster differs from Hemiaster 

 in possessing a postei'o-lateral fasciole, and in having the antero- 

 lateral ambulacra less divergent and lodged in deeper depressions ; 

 the anteal sulcus is also much deeper. 



Schizaster eurynotus, Agassiz. 



Syn. Echinus Spatangvs compressus et lapidescens in Melitensi 



topho, Scilla, Corp. Mar. tab. 7. fig. 1. 

 Echinus gladiatus vestitus et nudus Imperafi, Klein, Echinod. p. 35. 



tab. 27 A. 

 Spnfangus locu/wsus, Leske, no. 77- p. 227. 

 Spatangus canaliferus, Lamarck, Anim. sans. Vert. 2nd ed. torn. iii. 



p. 327; Grateloup, Foss. Ours. Dax, p. (i7. 

 Schizaster eurynotus, Sismonda, Mem. Echin. Foss. Nizza, tab. 2. 



fig. 3. p. 31 ; Agassiz and Desor, Ann. Sc. Nat. torn. viii. p. 21. 



scrie 3. 

 Spatangus Scillce, Desmoulins, Etudes sur les Echin. no. 24. p. 392. 



Test heart-shaped, depressed and rounded anteriorly, elevated 

 and pointed posteriorly ; ambulacral areas deeply excavated ; 

 the single ambulacrum long, deep, wider in the middle and 

 narrower at the anterior border, which is deeply grooved 

 by it: antero-laterals slightly /-shaped ; angle 52°; length 

 \^^^ inch : postero-laterals, angle 72°, short, /oths of an inch ; 

 apical disc with two genital holes near the posterior third ; 



