193 BREYiNIUS' MEMOIR 



V. Genus — Echinos-patagus, j8irey«2«s, 173i2. 



Heart-shaped Urchins, with inflated sides, the ambulacra on the upper surface lodged 

 in depressions of the test; the mouth anterior between the centre and tlie border; the 

 vent on the upper part of the posterior border in a direction oblique to that of the 

 mouth. This name was changed by Klein, 1734, to 7§?fl/««^MS, adopted by Lamarck 

 and all subsequent authors. As the genus Echinospatagm represents a natural family 

 rather than a genus, one of the forms figured by Breynius among his types ought to 

 bear this generic name, whilst the other genera might be readily arranged around the 

 central type form. 



VI. G^KS— EcHiNOBRissus, Brepiius, 1732. 



Small buckler-shaped Urchins more or less depressed, the mouth-opening near the 

 centre of the base, vent debouching into a deep dorsal sulcus, ambulacral areas petaloidal. 

 The specimen figured as the type of this genus is one of the most common Oolitic forms. 

 Still no author has cited this genus, and it appears to have been overlooked until Lamarck 

 described it under the name Nucleolites. 



VII. Genus — Echinodiscus, _5rej/wzas, 1732. 



Discoidal Urchins with the mouth and vent opening near each other at the base. 

 The ambulacra limited, petaloidal, and dorsal. Shell always flat ; border thin, entire, or 

 often indented or perforated. This genus was adopted by Gaultieri, 1742, and by Seba, 

 1758; by Leske and Davila, 1778. It was changed to Botula by Klein, 1734, and into 

 Scutella by Lamarck, 1801. 



The ' Dissertatio Physica de Polythalamiis, de Belenmitis, de Echinis,' by Breynius, is 

 a very scarce book. After endeavouring in vain to obtain it in commerce, I made known 

 my want to my friend Professor de Koninck, of Liege, who kindly gave me the copy I 

 now possess. In discussing many years ago the merits of this work with my old friend 

 the Rev. Robert Hepworth, M.A., he kindly offered to make a translation for my Mono- 

 graph of that portion of the dissertation which related to the classification of the Ecldno- 

 dermata, for which I heai-tily thank him, and I have now the pleasure of adding the 

 version as it came from his pen. I have inserted such references to the plates of this 

 Monograph as will help the reader to supply the absence of the original plates which 

 accompany the work of Breynius. 



