150 PEOi". p. M. Duncan's revision of the 



and double ambulacral floors o£ the tumid Clypeastroid, he did 

 not employ the term Echinanthus. On the contrary, he called the 

 forms (Nat. Disp.Ech. p. 28, pis. 17«,185, 19 «) Sectlo " Scutum," 

 species humile and altiim. 



Linnaeus called the tumid Clypeastroid Echinus reiiculatus ; 

 and Lamarck clearly differentiated the genus Glypeaster and 

 included both the tumid and the flatter species in it. 



Neither of these last-mentioned naturalists considered the 

 genus EcJiinantJius of Breynius to be of any value. 



In 1825 Grray resuscitated the term Eclnnanthus^ but applied 

 it not after the meaning of Breynius ; he made it include the 

 species termed Clypeaster by Lamarck. Neither Desmoulins 

 nor Agassiz and Desor followed Gray, but considered Lamarck's 

 generic term good and correct. However, in 1855 Gray called 

 all Clypeastroids, both flat and tumid, " Echinanthus,^^ in his Cat. 

 Eecent Ech. Brit. Mus. 



In 1825 Gray had founded the genus Echinolampas, and in 

 the Catalogue just referred to, p. 35, he again diagnosed that 

 genus, and placed Echmanthus (see also under Echinolampas 

 oviformis, Cat. Eec. Ech. Brit. Mus. p. 35) as a synonym. Here 

 an error crept in, and palaeontologists and zoologists have ever 

 ^■mcQ Qvci^Aojedi EcMnanthus in a different sense. The palaeonto- 

 logists, following the early part of the definitions of Echinanthus 

 by Breynius, have associated the word with the Cassidulidae ; the 

 zoologists have either associated the word with all the Clypeas- 

 troids, or have used it, following A. Agassiz, for the tumid 

 Clypeasters especially. 



Desor, in his Synopsis, 1858, associated the term Echinanthus 

 with a well-differentiated group, having all the characters of that 

 figure given by Breynius which has a longitudinally elongate 

 periproct placed siipramarginal — the figure which may have repre- 

 sented a Pygorhynchus. Echinantlius of Desor is a large genus, 

 and it is impossible to state, with truth, that it is not Echi- 

 nanthus according to Breynius. 



The distinction between the internal construction of the flat and 

 the concave based or tumid Clypeasters was shown by J. Miiller 

 in his 'Bau d. Echin.' 1854, p. 123. A. Agassiz, in his ' Revision,' 

 was so struck with the value of J. Milller's discoveries, that he 

 determined to make the tumid Clypeasters form a genus Echinan- 

 thus, Avhich he attributed to Breynius. The whole subject is con- 

 sidered with the usual great care of the author of that ' Kevision/ 



