no PSEUDODIADEMA 



tetragrammous Diadema with bigeminal pores. It very much resembles P. Brongniarti, 

 Agas., from the Grey Chalk, but is distinguished from the latter by having its upper and 

 under surfaces more depressed, the ambulacral areas narrower, their rows of tubercles 

 shorter, and those on the upper surface more rudimentary; the poriferous zones are much 

 wider on the upper foiu-th, and have the pores more largely bigeminal ; the base likewise 

 is more convex, wider, and less contracted than in P. Brongniarti. 



Locality and Stratigraphical Position. — P. variolare is found in the Upper Greensand 

 of Warminster, and the " Chloritic Marl " near Chard ; from the latter locality I have 

 specimens that represent the var. h., subnudam, and var. c, Boissi/i. The large specimen 

 was kindly communicated by the Rev. C. W. Bingham, of Binghams Melcombe, near 

 Dorchester; it was collected from the Upper Greensand of that neighboui'hood — the 

 precise locality is not recorded. 



Foreign Localities. — M. Cotteau has given a wide range to the distribution of this 

 species in France, and records — " Villers-sur-Mer, Cauville, Vaches-Noires, Dives, Saint- 

 Jouin (Calvados) ; Octeville (Manche) ; Fecamp, Le Havre, Rouen (Seine-Infcrieure) ; 

 Vimoutiers, Grace, La Perriere (Orue) ; Presagny pres Vernon (Eure) ; Berneuil (Oise) ; 

 Grandpre (Ardennes) ; La Fauche pres le Villard-de-Lans (Isere) ; Le Mans, La Raglasse, 

 Yvre-l'Eveque (Sarthe) ; Corze (Maine et Loire) ; Touvois (Loire-Inferieure) ; Angouleme 

 (Charente) ; ile Madame, Saintes (Charente-Inferieure). Assez abondant. Etage Ceno- 

 manien, commun surtout dans la zone a Scapldtes ceqiialis. — Lillebonne (Seine-Inferiem'e). 

 Rare. Etage turonien." 



In the Hils conglomerate, near Essen, Hanover. Desor. 



Uistorg.- — Figured for the first time by Brongniart in 1822, as Cidarites variolaris,m 

 his ' Geognosie Physique des Environs de Paris,' from a specimen collected at Havre in 

 the Upper Greensand. 



In the ' Catalogue raisonne des Echinides,' 1846, MM. Agassiz and Desor separated 

 certain varieties of this species from the type which they found in the museums of France, 

 under the names Diadema subnudum and D. Boissgi ; those, however, I have endeavoured 

 to demonstrate are merely varieties of P. variolare. 



