Vol. 62.] liRACHIOPOD HOMCEOMOEPHY, 435 



The above are the facts : they admit of varied interpretation. 

 For instance, the type of Terebratula antinomia may be selected out 

 of four specimens. Then the genotype of Pygope may be selected 

 from at least two species ; and it is not necessary that what is 

 selected to be the type of T. antinomia be taken to be the genotype 

 of Pygope. In fact, in view of Catullo's generic use of the term 

 Antinomia, it seems desirable to avoid this ; which is possible, as 

 there are five species out of which to select the genotype of 

 Antinomia. 



Prom among several attempted methods of arrangement, the 

 following seems to give the most satisfactory results in the 

 circumstances — diminishing as much as possible the difficulty of 

 identifying Catullo's most indifferent figures : — 



To select as the type of T. antinomia the specimen of which two 

 figures are given, namely Catullo's s, t [7]. To select as the type 

 of Pygope Catullo's fig. r ; this figure shows the perforation some- 

 what distant from the umbo. On this account, and because of its 

 shape, I identify this figure with Yalenciennes's Terebratula deltoidea 

 [36]. 



Then, out of the five species assigned to Antinomia by Catullo, 

 one, A. deltoidea, would consequently be withdrawn ; another, 

 A. diphya, is almost unrecognizable ; the same remark applies to 

 A. angulata. There remain then two species, A. angusta and 

 A. dilatata. The latter is a very definite form, though Catullo has 

 exaggerated its angles ; and I select it as the type of Antinomia, 

 believing it to be the same species as that which Catullo originally 

 called Terebratula antinomia, fig. r [7]. Hence, if this identification 

 be correct, the proper designation of the type of the genus will be 

 Antinomia antinomia (Catullo) ; although it must be remembered 

 that the genolectotype of Antinomia must be stated as Antinomia 

 dilatata, Catullo = T. antinomia, Catullo. 



Prom the statement of facts given above, it will be noticed that 

 the text-books and other systematic works are quite incorrect in 

 giving Terebratula diphya as the type of the genus Pygope. This has 

 arisen from the idea thatColonna's name overrode all others applied 

 to the perforate Terebratulids, and that the name diphya was 

 sufficient to cover all or most of the species of such perforate shells. 

 "Whatever view be taken of the number of species necessary, the 

 following statements at any rate are justified : — 



That T. diphya as a post-Linnean designation has not priority 

 over any names applied to perforate Terebratulids before 1835. 



That T. diphya is not mentioned as a species of the genus Pygope 

 by the founder of the genus : he knows only T. antinomia. 



That T. cor, Bruguiere, is the first post-Linnean designation for 

 a perforate Terebratulid. 



That when writers give the type of a genus, they should quote the 

 actual designation of the species referred to by the author of the 

 genus, not their interpretation of it, however certain they may 

 feel. 



