Genera of Recent Clypeastroids . 595 



easily determined. Leske included only four species in liis 

 genus (Jmmilis, alius, ovatus, orhiculalus), and of these 

 humilis equals rosaceus, L., and with its near relative alius 

 belongs in Clypeaster, where they were placed by Lamarck. 

 In 18:25 Gray lemoved ovatus to his new genus Echino- 

 lampas, and therefore orhiculalus alone is left to be the type 

 of Echinanthus. As this species is generally agreed to be a 

 Pygurus, Agassiz, the latter name becomes a synonym of 

 Echinanthus, unless it contains, as established by Agassi z, 

 one or more species not congeneric with orhiculalus, Leske. 



If, then, the name Echinanthus is no longer available for a 

 clypeastroid, and if Clypeaster, Lamarck, must replace 

 Echinanthus as used by A. Agassiz, what is the proper name 

 for the group called Clypeaster in the ' Revision ' ? Personally 

 I think it is practically impossible to separate the two groups. 

 It is true that the internal structure of the test of rosaceus 

 is strikingly different from its AVest-Indian ally suhdepressus, 

 Gray; but one cannot separate the Pacific forms by a corre- 

 sponding difference, and I think we must consider the 

 condition in rosaceus as simply a specific character. There 

 can be no doubt that increasing age brings an increasing 

 amount of calcareous matter for deposit in the test of clype- 

 astroids, and we must therefore be on our guard against 

 placing too much Aveigiit upon characters shown by the 

 internal structure of the test. If, however, it is desirable to 

 distinguish rosaceus generically from its nearest allies, the 

 latter may bear the name Stolonoclypus proposed by 

 A. Agassiz in 1863. The type of this genus I will here 

 designate as Clypeaster prostratus, Ra.vene\, = Echinanthus 

 subdepressa, Gray. 



The species called reticulatus by Linne is a more inexcu- 

 sable composite than rosaceus, as it is made up of two utterly 

 unlike clypeastroids : one is rosaceus itself, as clearly shown 

 by Sloane's figures to which Linne refers; while the other, 

 indicated by references to Gualthieri''s pi. ex. fig. D, is the 

 little Indo-Pacific species long known as Clypeaster scuti- 

 formis (Gmcl.). The difference in Linnets diagnoses of 

 rosaceus and reticulatus is so trivial that it needs no con- 

 sideration. Loven''s attempt in 1887 (/. c.) to delimit reticu- 

 latus was anticipated over a century earlier by Leske, who, 

 in 1778, clearly restricted the name reticulatus to the Indo- 

 Pacific form. As A. Agassiz showed this in the ' Hevision,' 

 I am at a loss to understand why he preferred the later name 

 scutiformis. 



Returning again to Linne's list, we find the fourth species 

 [orhiculas) recognized as a composite by its authoi-, who 



