252 ACROSALENIA. 



the equal size of the peristomal lobes, the magnitude of the apical disc, the compound 

 character of the sur-anal plate, and the great excentricity of the vent ; the fineness and 

 abundance of the granulation which adorns the test fully entitles it to the name decorata. 



Locality and Stratigraphical position. — I have collected this beautiful Acrosalenia from 

 the seams of yellow clay which traverse the CoraUine Oolite near Calne, Wilts, and from 

 the limestone of the same locality associated with Hemicidaris intermedia, Pseudodiadema 

 mamillanum, and Echinobrissus scutatus. The specimens in the Museum of Practical Geology 

 were collected by the officers of the Geological Survey, from the Coral Rag at Steeple 

 Ashton, Wilts, and near Abbotsbury Castle, Dorset ; some of the specimens in the British 

 Museum were obtained from the Coralline Oolite at Malton, Yorkshire. 



It has been recently collected by M. Cotteau, " dans les couches Kimmeridgiennes 

 inferieures des environs de Bar-sur-Aube."* 



History. — This species was first figured and described in the twelfth volume of the ' An- 

 nales des Sciences Naturelles,' by M. Jules Haime, as a remarkable urchin, " which he had 

 seen in the collection of the British Museum,, on the supposition that it exhibited characters 

 not met with in any known genus of sea-urchins, and that it combined the anal arrangements 

 of the Cassidulid^e with the usual characters of the CiDARiDiB, an union of structures 

 not hitherto observed." For this apparent anomaly, he proposed the genus Milnia, 

 which he considered as the type of a new family, designated by him Pseudocidarides, 

 and mistaking Malton, the locality from which this type specimen came, for Malta, 

 he considered it as probably a tertiary species. Mr. Woodward, who was previously 

 aware that the urchin thus erroneously described was an Acrosalenia, directed 

 Professor Forbes' s attention to the type specimen which was selected as the subject for 

 plate 3, Decade IV^ of the ' Memoirs of the Geological Survey,' where it is beauti- 

 fully figured, with full details of structure. My lamented friend, knowing that I had 

 collected this urchin in an excursion I made into Wiltshire, and being informed that 

 I was engaged in writing a description of it in my memoirs, kindly communicated a 

 proof impression of that plate to me : finding that it was deficient both in the anatomy of 

 the apical disc and in the structure of the spines, I supplied Professor Forbes with the 

 materials for both, which were then incorporated in his plate. It was fully described 

 in my 'Memoirs on the Cidaridse of the Oolites,' and afterwards by Professor Forbes 

 in his description of plate 3, Decade IV, of the ' Memoirs of the Geological Survey 

 of Great Britain.' As a foreign species, it was first found by M. Cotteau, and recorded 

 in his ' Note sur les Echinides de I'etage Kimmeridgien. du dep. I'Aube,' and after- 

 wards was described in his valuable work on Fossil Echinoderms.f 



* 'Bulletin Soc.G^ol. de France,' 2" serie, torn, xi, p. 355, 1854. 



f Cotteau, • Etudes sur les Echinides Fossiles du departement de I'Yonne.' 



