EVECHINUS. 281 



EVECHINUS. 



Verrill, 1871. Trans. Conn. Acad., I, p. 583. 

 Type-species, Echinuschloroliciis Valenciennes, 1846. Voyage "V6nus," Zoophytes, PI. VII, fig. 2. 



The revival of the name Heliocidaris by Mortensen (1903, "Ingolf" Ech., 

 pt. 1, p. 116) leads to some rather interesting results as to the proper use of that 

 name. Mortensen's remarks on the subject are as follows: 



"In 'Cat. rais.' the species variolaris Lamk., paucituberculatus Blainv., and 

 chloroticus Val. are enumerated under the genus Heliocidaris. For the first of 

 these species the older name of Stomopneustes must be used; according to Agassiz 

 (Rev. of Ech.) paucituberculatus is synonymous with this. As far as I can see, 

 chloroticus must then be the type of the genus Heliocidaris; the name Evechinus 

 Verr. (1871) must then be dropped as being a much younger one, and I cannot 

 but wonder, why Agassiz, who otherwise takes great care to reestablish the 

 oldest names, has here preferred the name of Evechinus." So far as the data 

 given in this paragraph go there is no escape from Mortensen's conclusion but 

 why has he omitted to mention the five other species included in Heliocidaris 

 by Agassiz and Desor? Presumably it is because he considers the first named 

 valid species the type of the genus and hence does not consider it necessary to 

 even mention those which follow chloroticus. It is hardly necessary to say that 

 the selection of the type of a genus is not so simple a matter and in this case is 

 by no means easy. Agassiz and Desor included in their genus, besides the three 

 species mentioned by Mortensen, the following five: Echinus margaritaceus 

 Val., E. erythrogrammus Val., E. ornalostoma Val., Heliocidaris mexicana Agass., 

 and Echinus mirabilis Agass. The last named species was subsequently made 

 the type of Phymechinus by Desor, while Heliocidaris mexicana is now known 

 to be based on a specimen of Echinometra lucunter L. In 1863, A. Agassiz 

 established the genus Toxocidaris, naming as the first species Echinus Delalandi 

 Val., which was subsequently shown to be identical with E. erythrogrammus Val. 

 In 1871, therefore, when Verrill proposed Evechinus, Heliocidaris contained 

 chloroticus, margaritaceus, and omalostoma, and Verrill acted quite within his 

 right in making the first of these the type of a new genus, if he chose. The type 

 of Heliocidaris therefore must be either margaritaceus or omalostoma and fortu- 

 nately, whether one accepts for the former, Koehler's genus Sterechinus or rejects 

 it, as I do, as not distinguishable from Echinus, margaritaceus is eliminated, 

 and omalostoma is therefore the type of Heliocidaris. There is no question that 

 omalostoma of Valenciennes is identical with tuberculatus Lamarck and thus 



