m 2038. FOSSIL CR/A'O/D GEXU8 HOMOCRiyVS^KIRK. 475 



the case, paleontologists may well be bound by more exact and rigid 

 rules than workers in recent forms. In paleontology no hardship 

 would be wrought, I think, if the fu^st species described were always 

 to be held as the genotype. This ruling, of course, should be effective 

 only in those cases where the original author's choice of a genotype is 

 not specified or indicated. In the very nature of things it is evident 

 that an author, unless giving his species an arbitrary arrangement, 

 tends to place his most characteristic species first. The choice of the 

 first species as genotype is the only wholly satisfactory method of 

 procedure, and obviates much of the confusion that is almost sure to 

 follow the apphcation of any other method. A number of cases 

 might be adduced where the choice of a second type-species by sub- 

 sequent authors has resulted in an absolute misconception of the true 

 character of a genus. 



It seems to me that in no case is the changing of the type-species 

 from the one specified by the author of the genus, or if not definitely 

 specified, the first species described, justified. In case such a species 

 be unrecognizable, and the type material certainly destroyed, the 

 genus should lapse, as in the case of a species under similar condi- 

 tions. When, as frequently happened in former times, no species 

 was chosen as the type of the genus, it might seem that one should 

 seek the intent of the author, as expressed by his choice of species 

 referred to the genus, and pick out a species other than the first 

 described, for the reason perhaps that better material of that par- 

 ticular form has since become available, or for some other reason. 

 Such reasoning is inadmissible, however. In case a genus were de- 

 scribed and the fu-st species is represented by such poor material 

 that its structure could not and can not accurately be determined, 

 the chances are that the other species refeiTed to the genus are not 

 congeneric. 



In the present case Homocrinus parvus, as the first species defined 

 under the genus, will be held as the type. No excuse is required for 

 this action. This is peculiarly an instance that shows the impro- 

 priety of allowing a subsequent writer a voice in the delimitation of a 

 genus by permitting him the choice of the type-species. Homocrinus 

 parvus may have been incorrectly defined — as were the types of most 

 of the early genera. The figures and analysis of the cup as given 

 by Hall (1847, pi. 41, figs. Ic-d) and partially reproduced in this 

 paper, surely give a present-day worker an inklmg as to the true 

 structure of the animal, however. The figure here copied from HaU 

 is fairly accurate. The analysis of the cup is inaccurate in that the 

 brachials are indicated as arising between the radials. A compound 

 radial is unmistakable in both instances, however. Moreover, the 

 types of Homocrinus parvus have been at all times accessible in the 

 American Museum of Natural History and a fair amount of authentic 



