^^^' 54'] ^^' ^' '^' JUKES- BEOWNE ON HOL ASTER ALTU8. 247 



specimens wMch from their aspect come from the craie marneuse 

 of France/ 



The figure given by Agassiz shows some other characters which 

 .are quite as important as those he mentions : — 



(1) It is of small size, its dimensions being : Length 1^ inch 



(30-8 mm.), breadth 1^ inch (28 mm.), height 1 inch 

 (25 mm.). It is therefore of great proportional height, 

 but it is stated that other examples are not so high as that 

 figured. 



(2) The posterior border, as viewed from the side, is truncated 



vertically. 



(3) The apex is excentric anteriorly, the distance from it to the 



posterior border being about two-thirds of the length of 

 the test. 



It will be seen that the English specimen delineated in PI. XXIY, 

 :fig. 4, agrees very closely with Agassiz's specimen in its dimensions 

 ^nd general characters. 



But a closely-allied form was described by Eenevier in 1867 under 

 the name of Holaster Bischoffi,^ and it was afterwards figured by 

 P. de Loriol-Lefort.^ The descriptions of this species given by both 

 -these writers will apply equally well to Agassiz's B. alius, except 

 in three respects : it is still smaller than alius ; it is described 

 as subcylindrical, and ' rather flattened ' or ' not very convex ' on 

 the upper surface. From the figure this seems to mean that the 

 posterior ridge is nearly parallel with the median line of the under 

 ^surface, the height of the test being nearly the same above the vent 

 as at the apex. 



Specimens which agree closely with P. de Loriol-Lefort's figure 

 and description of H. Bisclioffi are not uncommon in the Cenomanian 

 of Beer Head, and were mentioned in a former paper ^ as either 

 a well-marked and unusual variety of Holaster suhglobosus or a 

 distinct species. A brief description of the form was there given. 



Being in some doubt whether to identify the Wilmington examples 

 ;as H. alius or H. Bischoffi, and in more doubt as to whether these 

 forms were really distinct species, I sent five specimens to M. P. de 

 Loriol-Lefort, and asked him to pronounce an opinion. His reply, 

 which he kindly allows me to publish, is as follows : — 



' Je les ai compares avec des exemplaires de VHolaster alius, Ag., 

 du Cenomanien de Eouen, et avec des individus de VHol. BiscJioffi, 

 •de Cheville. Je crois que vos exemplaires de Wilmington doivent 

 plutot etre rattaches a VHol. alius. JJHolaster Bischoffi est une 

 petite espece, un peu cylindrique, etroite, moins large que I'autre ; 

 .elle est rare dans nos gisements. . . .Ceux que je viens d'examiner a 

 nouveau ressemblent absolument aux deux plus petits exemplaires 

 •que vous m'avez envoyes (ceux de la roche dure) ; mais ces derniers 



i^BuU. Soc. Vaud. Sci. Nat. vol. ix (' Faune de Cheville/ p. 446). 

 2 ' Echinologie Helvetique,' vol. ii (1873) p. 333, pi. xxviii, figs. 1 & 2. 

 ^ ' A Delimitation of the Cenomanian,' Quart. Journ. Geol. Soc. vol. lii 

 (1896) p. 144. 



