GKAPTOLITE8 OF NEW YORK. I'AUT 1 B97 



we had occasion to verify in t)Ui' material, in regard to Salter's figures, in et)m- 

 bination with other characters, it must be concluded that Salter's first two 

 drawings and his description [1853, p.87j can apply only to the form latei" on 

 described as D. gibberulus by Nicholson. Of the two drawings com- 

 prised in a later publication [1863, p. 137, fig.l3a, 13b] under this name, the 

 former is surely the Didymograptus. the latter represents probably a Tetra- 

 g r a p t n s b i g s 1) y i . This conclusion is supporte dby the fact that a long 

 nema is noticeable in the first two drawinjjs and is also cited in the original 

 description ; for, Avhile the species of D . gibberulus are notable for their 

 long nema, one will not notice this filiform snspensory organ among hundreds 

 of specimens of T e t r a g r a p t ii s b i g s b y i . 



It is, hence, apparent that Salter had before him, at the time of the 

 original description of D . c a d u c e u s , the form which, later on, Avas desciibed 

 and is generally known as D. gibberulus Nicholson, a name which has, 

 then, to give Avay to Salter's older name. Salter's specimens were obtained by 

 Dr Bigsbyfrom the " Lauzon Precipice," and came therefore from the Quebec 

 shales. Hall had evidently no examples of this species in his material from 

 the Quebec shales, or he Avould not have failed clearly to recognize the differ- 

 ence between his T e t r a g r a p t u s b i g s b y i and D. caduceus Salter. 

 He states in regard to the former; " These forms resemble the Graptoli 

 thus caduceus of Salter Avhich \vas obtained by Dr Bigsby from ' the 

 Lauzon Precipice,' and I have hesitated in regard to making of them a 

 new species." The writer has found D . (gibberulus) caduceus in the 

 Deep kill shales, so that there can be no doubt of the presence of that species 

 on this side of the Atlantic. 



R. Etheridge jr figures both forms here discussed as Tetragraptus 

 b r y o n o i d e s, considering D. caduceus as a synonym of that species. 

 It is clear, however, from his description, that he Avas aware of the constancy 

 of the differences of the two forms, united by him under that name, and he 

 suggests that Salter's name might be retained as a varietal designation for 

 such forms as those shoAvn by his figures 3 and 4, Avhich represent specimens 

 of D . o- i b b e r u 1 u s Nicholson. 



