Ill 



(including Opechinus and Genocidaris), Salmacis (with Salmacopsis as a subgenus), 

 Mespilia, Microcyphns, Amhlypnenstes, Goniopneiistes and Holop neustes, the other, Gly- 

 phocyphincE, including Trigonocidaris and the fossil genera: Glyphocyphus, Dictyo- 

 pleiirus, Arachnioplenrus, Ortholophus, Paradoxechinus, Echinocyphus, Zeuglopleurus, 

 Lepidopleiirus, Leiocyphus and Coptophyma. In his „Revision of the British fossil 

 Cænozoic Echinoidea ' ') Gregory suggests that Temnechinus, as having no true pits, 

 ought to be transferred to the Glyphocyphinœ. In the „Treatise on Zoology", how- 

 ever, he retains this genus among the Temnopleurinœ ; further the subfani. Glypho- 

 cyphinœ is restricted so as to comprise those genera „in which the compound 

 ambulacral plates are composed of three primaries" , the genera „in which the 

 compound ambulacral plates are composed of two primaries and an intermediate 

 demi-plate" being made another subfamily, Ortholophinœ; to the latter subfamily 

 Trigonocidaris is also referred, though with a mark of interrogation (Op. cit. p. 312). 

 According to Agassiz („Blake"-Echini. p. 38) „the presence of pits and sutures 

 is a feature only developed with age, and the transition is insensible between the 

 types in which the pits and sutures are formed by the modification of a flat sur- 

 face due on one side to the thickening or elevation of nearly the whole plate, or, 

 on the other, of only a portion of it". I cannot agree with Agassiz herein; I find 

 the pits very distinct in very small specimens, as small as, upon the whole, it is 

 possible to determine with certainty. — The distinction between true and false pits is 

 thus certainly of great importance, and I quite agree with Duncan and Gregory that 

 the genera of the Temnopleiiridœ must be classified upon this structure. The forms 

 with true pits have also the plates united by ..dowelling", and they further agree 

 in having, generali}', smooth plates without superficial ornamentation (in this 

 respect, however, Pleurechinus scillce is a very conspicuous exception). These 

 genera : Temnopleurus, Pleurechinus, SaUnacis, Salmacopsis, Mespilia, Microcyphus, 

 Amhlypneustes, Goniopneustes and Holopneustes evidently form a natural group and 

 must form a subfamily Temnopleurinœ. The other genera: Hypsiechinus, Prion- 

 echinus^), Genocidaris, Trigonocidaris, Temnechinus and Opechinus differ from the 

 Temnopleurinœ in having no true pits and the plates not united by dowelling. 

 Duncan evidently contradicts his own results when saying in his diagnosis of the 

 whole family Temnopleuridœ that the plates are united by dowelling. In his paper 

 „On the genus Pleurechinus" (p. 454) he emphasizes that in Temnechinus „none of 

 the remarkable minute structures of the test of Temnopleurus are present" (which, 

 I can state, is correct, after examining an excellently preserved fragment of temn- 

 echinus Woodi (Agass.) in the British Museum), and in another paper „On some 

 Points in the Anatomy of the Temnopleuridœ'' ^) he says with regard to the recent 



') Proe. Geologists Assoc. XII. 1891. p. 30. 



'') Arbacina {Cotlaklia] forbesiana has been shown by de Membre to be a Prionechinus („Siboga"- 

 Kch. p. 71). 



') Ann. Nat. Hist. tJ. Scr. I. 1888. p. 11Ü. 



