598 ilr. H. L. Clark on the 



Bull. Inst. Egypt, (4) iv.) confirms A. Agassiz^s view that 

 the two are identical, it is desirable to have decided which is 

 the typical form. 



Leske^s genus Echinocyamus contains thirteen nominal 

 species, all based on Van Phelsum^s figures. Lamarck 

 (1816) includes the same group, so far as he recognizes them 

 at all, in his genus Fibularia. The two names were used 

 interchangeably for many years, some writers using Leske^'s 

 and others preferring Lamarck^s, until, in 1847, Agassiz 

 and Desor (Ann. Sci. Nat. (3) vii. pp. 140-142) restricted 

 Echinocyamus to the flat forms {'' Oursins plat") and Fibu- 

 laria to the high ones {" Forme subspherique ou ovo'ide "). 

 As angulosvs is the only one of Leske's thirteen species 

 which they mention, and as it stands first in their list of 

 Echinocyamus species, it may well be considered the type of 

 that genus. Under Fibularia they mention two of Lamarck's 

 species, ovulum and trigona ; but as the former is now 

 generally considered a synonym of the latter, trigona is 

 doubtless the type of the genus. 



Were the history of the name Echinarachnius exactly as 

 recounted in the ' Revision of the Echini,' it would be im- 

 possible for us to retain it for the sand-dollars in the sense 

 in which it has been used for seventy years ; but fortunately 

 quite another interpretation of Leske's use of the name than 

 that given in the ' Revision ' is not only permissible, but is 

 apparently more reasonable. On p. 153 of his ' Additamenta 

 ad Klein ' Leske refers to a clypeastroid under a '■' Genus 1 " 

 which he says Van Phelsura called Echinarachnius, and on 

 the next page (154) he describes it as '' Species 74, Echin- 

 arachnius." Further on he says it is identical with Echinus 

 placenta. L. Van Phelsum, however, did not call the animal 

 Echinarachnius, and oh p. 8 Leske himself translates Van 

 Phelsum's colloquial name as Arachnoides, which is Klein's 

 " Genus unicum'^ and obviously Leske's " Genus 1." Is it 

 not clear, then, that it is no mistake of Leske's in calling 

 Echinarachnius a species rather than a genus ? He evidently 

 intends to retain Klein's name Arachnoides for the genus, 

 and as Klein gives no specific name, Leske proposes echin- 

 arachnius, but states that it is equivalent to placenta, L. 

 Gray (1825, op. cit.) errs in attributing the genus Echin- 

 arachnius to Leske, for he was himself the first writer to use 

 the name as a generic term. He includes three species in 

 his genus — placenta, L., and Scutella parma and lenticularis, 

 Lamk. In 1841 Agassiz restored placenta to the genus 

 Arachnoides and put lenticularis in Scutellina, so that parma 

 becomes the type of Echinarachnius. As placenta is the only 



