TEMN0PLE1 l : 1 1 > - 1 :. 37 



'n:.M.\ni-Li;ri;i[).i: 



Duncan* 1ms. in interesting articles on the pits and sutures of Temno- 

 pleurus and on the structure of Pleurechinus, called attention to the im- 

 portant differences existing between the Temnopleuridae of the type of 

 Temnopleurus proper and its allies, and such genera as Temnechinus and 

 Trigonocidaris, which have been associated with them. 



He proposes to place on one side the genera Pleurechinus, Temnopleurus, 

 Salmacis, and Amblypneustes, which' have true pits, and on the other side 

 the genera Temnechinus, Trigonocidaris, Paradoxechinus, and Glyphocy- 

 phus, which have raised ribs. 



The structural difference so well pointed out by Duncan is an important 

 one; he says be was unable to find, in the specimens of Temnechinus from 

 the Crag which he examined, any trace of the remarkable "deep inward 

 undermining or penetrations of the test " of Temnopleurus. The specimens 

 of Temnechinus maculatus of different sizes which 1 have examined show 

 no trace of pits, nor of this system of dowelling at the junction of the 

 plates. I have also again examined specimens of the recent Trigonocidaris 

 albida, and do not find in that species either the sunken pits of Temno- 

 pleurus proper or the dowelling. 



Duncan and Sladen t have figured in the fossils of Western Sind two other 

 genera closely allied to Trigonocidaris : Dictyopleurus and Arachnopleurus, 

 in which the grooved and pitted ornamentation of the tesl is produced 

 entirely by ribs and elevations. The peculiar structure of the ornamentation 

 of the genus Progonechinus shows how difficult it may become to maintain 

 the distinction suggested by Duncan. 



I had already called attention iii the Revision of the Echini, p. 286, to 

 the character of the ornamentation of the test of some of the Temnopleuridae, 

 and to its probable derivation from a re simple type of ribbed ornamen- 

 tation, such as is formed by the radiating arrangement of miliaries ami 

 secondaries round the primar} tubercle of >ome of the Triplechinidae and 



• e \| Di e Points in the Morphology of the Tesl of Temnopleuridre, Journal I. inn. 



ndon, L882, Vol. XVI. p. 343. On the Genua Pleuiechinn . I rnal I. inn. Soc. 



London, is--'. Vol. XVI. p. ii:. 



t Mem. Ueol .Survey of India, St. XIV., VoL I.. The Fossil Echinoidi ■■. I 

 cutta, i*-j. 



