116 Dr. T. Wright on Fossil Echinoderms 



ft Boutonnet pres de Montpellier, et en Italic dans les couches, 

 qui paroissent appartenir au calcaire coquillier grossier*." 



EXPLANATION OF PLATES IV. V. VI. AND VII. 

 PLATE IV. 



Fig. 1. Cidaris Melitensis: a, the upper surface; b, side view of the am- 

 bulacral and interambulacral areas, natural size ; c, an iuteram- 

 bulacral plate, and a portion of an ambulacral area with the 

 poriferous zones, magnified. 



Fig. 2. Echinus Duciei : a, upper surface ; b, side view, natural size ; c, the 

 form of the mouth-opening, showing the disposition of the mar- 

 ginal notches ; d, the five jaws and teeth " in situ" imbedded in 

 a mass of rock ; e, the apical disc, showing the arrangement of 

 the genital and ocular plates ; /, two interambulacral plates, and 

 a portion of a poriferous zone, magnified. 



Fig. 3. Echinolampas Deshayesii : a, the upper surface ; b, the under sur- 

 face, natural size ; c, a portion of the test, showing the tubercles, 

 magnified ; d, a portion of an ambulacral area, and poriferous 

 zones, magnified. 



PLATE V. 



Fig. 1. Brissus latus: a, the dorsal surface, reduced one-third in size; 

 b, the apical disc, magnified ; c, the perforated tubercles, with 

 their crenulated bosses and encircling granules, magnified. 



Fig. 2. Brissus oblongus : a, the upper surface, showing the petaloid am- 

 bulacral star and peripetal fasciole ; 6, the under surface, showing 

 the subanal fasciole, natural size ; mouth, and the trajet of the 

 naked basal portions of the ambulacra ; c, the tubercles, and 

 their circles of granules, magnified. 



Fig. 3. Schizaster Parkinsoni : a, the upper surface, showing the petaloid 

 ambulacral star, the peripetal and lateral fascicles, the natural 

 size ; b, a portion of the peripetal fasciole, with the boundary 

 granules, magnified ; c, a portiou of the poriferous zones, mag- 

 nified. 



PLATE VI. 



Fig. 1. Brissopsis Duciei : a, the upper surface, showing the petaloidal 

 ambulacral star, surrounded by the peripetal fasciole, reduced 

 one-third ; b, six plates with small poriferous tubercles from the 

 anteal sulcus ; c, form of the pores, and arrangement of the tuber- 

 cles in the poriferous zones ; d, the larger perforated tubercles, 

 and their crenulated bosses with their circlets of granules ; e, a 

 portion of the peripetal fasciole, showing how distinctly it is 

 defined from the rest of the surface by rows of granules. 



Fig. 2. Brissopsis crescenticus : a, the upper surface ; b, the under surface, 

 natural size ; c, the arrangement of the pores, near the apical 

 portion of one of the zones. 



Fig. 3. Schizaster Desori : a, the upper surface ; b, the under surface, 

 natural size ; c, the perforated tubercles, with their circlets of 

 granules and crenulated bosses, magnified. 



Diet. Sc. Nat. tome xxv. p. 453. 



