from the Lias and Oolitet. 21 



clay near the Tctbury Road Station, Great Western Railway, 

 closely resemble this form ; but as no entire specimen, that we are 

 aware of, has been found, it is impossible to state whether it has 

 a wider range in the higher beds of the lower division of the 

 Oolites or not. 



We dedicate this species to our friend M. Bouchard Chantereaux 

 of Boulogne, to whom we are indebted for some beautiful and 

 rare specimens of Echinoderms and other fossils from the rocka 

 of the Boulonnais, most kindly contributed by him to aid us in 

 the composition of these memoirs. 



Hemicidaris minor, Agassiz. PL I. fig. 3, a-c. 



SYN. Hemicidaris minor, Agassiz, Catalogus Systematicus, p. 9 ; 



Agassiz and Desor's Catalogue raisonne des Echinides, Annales 



des Sci. Nat. torn. vi. p. 339. 

 Acrosalenia rarispina, M'Coy, Ann. of Nat. Hist. 2nd Series, vol. ii. 



p. 411. 



Test hemispherical above, flat at the base; ambulacral areas 

 slightly flexuous, not prominent, with six large tubercles at 

 their base, and four rows of small unequal-sized granules in 

 the middle, diminishing to two rows in the upper part of the 

 areas ; interambulacral areas three times the width of the am- 

 bulacral, with three primary tubercles on the upper surface 

 and three smaller ones at the base ; the wide intertubercular 

 spaces are covered with small distinct nearly equal-sized gra- 

 nules, which form complete circles around the margins of the 

 areolas of the primary tubercles ; the apical disc is of mode- 

 rate size, and its ovarial plates are covered with a delicate gra- 

 nulation ; base flat, mouth-opening large and decagonal ; 

 pores arranged in the avenues in a single file throughout. 



Height / G ths of an inch, transverse diameter ? %ths of an inch. 



Description. This beautiful little Urchin was first discovered 

 in the etage Bathonien of Langrune, Calvados, the true equiva- 

 lent of the Great Oolite of English geologists ; it was entered 

 in M. Agassiz's ( Catalogus Systematicus* ' as Hemicidaris minor , 

 from specimens sent to him by M. Michelin ; it afterwards found 

 a place in the ' Catalogue raisonne des Echinides ' of Agassiz and 

 Desor, accompanied with this remark : " Se distingue entre tous 

 les Hemicidaris par les tubercules tres espaces, dont il n'y a que 

 deux ou trois dans une rangee. Terrain Jurassique de France. 

 Michelin." Professor M'Coy, in his paper " On some new Me- 

 sozoic Radiataf," afterwards described this Urchin under the 



* Catalogus Systematicus Ectyporum Echinoderm. FOM. Mus. Neoco- 

 mensis, 1840. 



t Annals of Natural Ilistorv, 2nd Series, vol. ii. p. 411 



