■'^"f^' ] Chapman, What are Type Specimens'^ 63 



Typks of Genera. 



Genotype (Schuchert). — The selected tyjie species (not 

 specimens) upon which the genus is based. 



To give a practical illustration of the use of the type names 

 above cited, let us take one of M'Coy's types — viz., that figured 

 and described under the name of Squalodon ivilkinsoni. The 

 original specimen, a molar tooth, was first figured by Sir F. 

 M'Coy in 1864,* and re-figured in 1875.! This tooth, forming 

 the basis of the original description, is the holotyj^e. Sul)- 

 sequently, in 1870, the same author figured and described another 

 tooth ("anterior tooth") under the same name. This speci- 

 men, as a supplementary type, would be termed a plesiotype, 

 not having been used in the original description. If, however, 

 it had been so used it would have formed either one of the two 

 types employed, if the author had considered them o^ equal 

 value in the description, and hence called cotypes ; or it co\ild 

 have been used for comparative purposes in the original de- 

 scription, when it would form a paratype in conjunction with 

 the holotypc. Quite recently Dr. T. S. Hall has reviewed 

 the position of the squalodont teeth of southern Australia and 

 New Zealand, and. in enlarging on the diagnosis of Sqvalodon 

 wilkinsoni, which he places, by the way, in a new genus — 

 Parasqucdodon, T. S. Hall — that author figures some additional 

 si)ecimens. Thus, in the paper and plate referred to, J figures 

 I, 3, and 4 are additional plesiotypes. Further, since this 

 species has been so well cared for, there would be no difhculty 

 in choosing a neotype, did such necessity arise through disaster, 

 for one of the plesiotyj)es here enumerated could be then regarded 

 as worthy of replacing the type as a neotype, and could be found 

 either in the National Museum collection, in Dr. Hall's col- 

 lection, or in the (Geological Department of the Adelaide 

 Tniversity. 



In dealing with the subject of typical specimens, if Fate snulc 

 uj)on us and we be fortunate enough to find either a molar, 

 l^remolar, or incisor of Parasqiialodon wilkinsoni in the exact 

 stratum which furnished the original holotype, at Castle Cove, 

 Otway coast, we may term these topotypes. In the event 

 of a recognized worker in this special group of fossils producing 

 a similar specimen to the type, and after careful examination 

 agreeing as to their identity, that second (compared) sjiecimen 

 may be defined as a hom'jeotype. Any further specimens fiom 

 Castle Cove that had been named by M'Coy, not necessarily 

 from the same stratum, would be metatypes : and if obtniiK-d 



* (ieol. Mag., vol. iv. (1867), pi. viii., fig. r. 

 t •• Prod. I';il. Vict.." dec. ii. (1X75), pi. \i.. ligs. i, i,;-</. 

 + Vrnc. Koy. Soc. \'ict., vol. xxiii. (N.S.). jU. ii. (igi 1), ])]. xx.wi. 



