﻿FROM THE MEDIAL CHALK. 



223 



Galerites albogalerus, Desor. Synopsis des Echinides Foss., pi. xxv, 1857. 

 Echinoconus coxicus, Cotteau. fichinides du Depart, de la Sarthe, pi. 47, 



figs. 1—3, 1860. 



Diagnosis. — Test much elevated, conoidal, larger anteriorly than posteriorly ; slightly 

 angular and rounded at the border ; base flat ; single inter-ambulacrum tumid and re- 

 curved ; vent large, oval, infra-marginal ; mouth-opening central, periostome decagonal, 

 armed with five pairs of dentiferous jaws ; ambulacra straight, narrow, doubly lanceolate ; 

 pores small, unigeminal, in oblique pairs, which become trigeminal near the periostome ; 

 interambulacra wide, angular ; tubercles on both areas small, homogeneous ; granules 

 abundant, unequal, sometimes elongated and prominent ; apical disc small, quadrangular, 

 very solid. 



Dimensions. — Height, one inch and five tenths ; latitude, one inch and four tenths. 



Description. — I recognise three well-marked varieties of form in this Urchin, which 

 have been described as distinct species by different systematic authors : these are, 

 according to my reading of the matter, as follows : — 



Forma a. Conica. — This may be regarded as the normal form, and as such it is figured 



as the type of the species. 

 Forma |3. Pgramidalis. — Desor, ' Monographic des Galerites/ PI. I,' figs. 1 — 3 ; 



d'Orbigny, Paleontologie PI. 1000, figs. 5 — 7. A small 



test, with pyramidal elongation of the vertex. 

 Forma y. Angulosa. — Desor, ' Monographic des Galerites,' PI. 4, figs. 5 — 7, a 



depressed, elongated, and angular variety of Conica. 



Description. — This is the most typical of all the Echinoconi, and has been well 

 figured and described by most classical authors who have described the different forms 

 of this genus. It is the true Echinoconus vere conicus of Breynius, 1732 ; two years later 

 it was figured and described as Conulus albo-galerus by Klein, on account of its supposed 

 resemblance to the white caps worn by the priests of Jupiter. Lang figured it in 1708 

 as Echinomctritis in his ' Historia Lapidum figuratorum Helvetia?,' and Bourget in his 

 ' Traite. de Petrifactions/ as the Ecldnite conoide, whilst Lamarck made it the type of his 

 new genus Galerites, reserving for it the specific name albo-galerus, given by Klein, by 

 which it has been known to the present time. 



The general form of this Urchin is conical, varying in different specimens from a tall 

 pyramid, with very steep sides, to a short one with inflated walls ; the base is flattened, 

 its circumference slightly pentangular, the greatest width corresponding to the region of 

 the anterolateral ambulacra ; the basal angle is more or less rounded, and the single 

 inter-ambulacrum tumid and recurved. 



The ambulacral areas are doubly lanceolate, and built up of minute plates, which in 

 the upper part of the area are often cuneiform in shape, irregular in size, and some- 



