GENERA. AND GROUPS 01" THE ECHINOIDEA. 119 



forming the canals for the water-system ; actinally the ambulacra 

 and infcerradia much pierced by pores, less so dorsally. Tentacles 

 heteroj)odoas. Spheridia two, covered, in each, ambulacrum. 



Genus Clypeaster. 



Subgenus Monostychia. 

 Genus Diplothecanthus. 

 Plesiantkus. 

 Anomalanthus. 



The generic name Clypeaster originated with Lamarck, Syst. 

 Anim. s. Yert. 1801. Previously Breynius, 1732, ' Schediasma de 

 Echiais Metbodica disponendis,' p. 59, placed a genus Ecliinan- 

 tlius as one of the seven into which the Echinoidea could be divided. 

 His definition was, " EcTiinanthus est Echinus cujus apertura pro 

 ore est prope centrum, pro ano in, vel ad marginem longissimeab 

 ore distantem." This is completely inadequate, and it naturally 

 led him to combine several forms witbin tlie group, which really 

 have no generic resemblance or aflBnity. Breynius gave figures of 

 his types, and it is perfectly evident that his first form of JEchin- 

 anthus is a well-growu Echinolampas oviformis. (Tliis was 

 reproduced in after years by Klein, Nat. Disp. Ech. tab. xx. 

 figs, c-d; compare with Breynius, tab. iv. fig. 1.) 



A second form included resembles Pygorhynchus, and a third 

 is a Cassidulus. Breynius gave no figure of a Clypeaster or 

 of an Echinanthus as accepted by modern naturalists ; but he 

 refers to Eiumphius, 1705, ' Amboiusche Eariteitkamer,' pi. lix. 

 fig. D, stating that his figure of Echinanthus agrees with the 

 type of Eumphius ; but this last is a miserable figure of a fossil 

 Clypeaster alius. Again, the figure in Eumphius's tab. xiv. fig. 3, 

 is said by Breynius to represent an Ecliinantlius, but it is a Cassi- 

 duloid. However, Breynius refers to Sloaue, Nat. Hist. Jamaica, 

 t. ii. tab. 212. figs. 6-11, and sta'.es that the figures also relate to 

 his EcMnanthus. They are those of the tumid Clypeastroid. It is 

 interesting to note that Breynius remarked that the teeth of this 

 form diff'er from those of Echinometra, and that there are within 

 the test "trabes perpendiculariter ercct^is." 



It is clear that Breynius did not separate the toothless EcJiiiio- 

 laivpas and Cassiduloids from the gnathostomous Clypeastroid. 

 It is therefore useless to prolong the discussion regarding his 

 priority. 



Klein came next, and although he employed the figures of 

 Breynius and added, op. cit. pi. xxix., capital figures of the supports 



