70 Proceedings of the Royal Society of Victoria. 



of the sicula, it is improbable that the sHght extension of the 

 periderm represents a median azygos hydrotheca, and from the 

 fact that it is clearly seen to be closed below in some specimens 

 it cannot represent the upper open end of the sicula. The figures 

 in the Prodromus, above alluded to, apparently show the first 

 two hydrothecje in contact by their inferior margins throughout 

 their whole length, and since they are cei'tainly in contact in 

 most specimens for a part of their length, there is nothing 

 inherently improbable in this occurrence ; still, I have not seen 

 an instance of it. Sir Frederick McCoy has kindly allowed me 

 to examine closely the examples of this species in the ISTational 

 Museum, including the two larger specimens figured in the 

 Prodromus. The specimen from which figures 5 and 5^ were 

 taken could not, however, be identified. The two larger specimens 

 figured are not sufficiently well preserved to allow of an expres- 

 sion of opinion one way or the other. All the well-preserved 

 specimens in the Museuin showed the character I have drawn 

 attention to. Nearly 150 specimens in my own collection and 

 ninety-six in the collection of Mr. G. B. Pritchard (which were 

 kindly placed at my disposal by him) showed the same structure. 

 Mr. J. A. Atkinson has obligingly examined about fifty examples 

 which he has from Castlemaine, and has shown me four in which 

 the separation of the distal ends of the margins is not clear ; but 

 as the examples are not very well preserved, and are, I think, 

 slightly distorted, they cannot be taken into account. Thus in 

 fully 300 examples which were in a fairly good state of preserva- 

 tion the character is constant, and the only specimens in which 

 it was not clearly shown were either damaged, weathered, or 

 distorted by cleavage. 



Dr. Perner has recently figured two examples from Bohemia,* 

 which are, however, so imperfectly preserved and distorted in the 

 sicular region that the original form of this portion is quite inde- 

 cipheraljle. 



Synonymy. 



Considerable confusion exists as to the generic position and 

 correct name of this species. Didy)nog7-aptns cadnceiis was 



* Etudes sur les Graptolites de lioh.'ine, 2ii;ine paitie, pi. vi., fisfs. 0, 10, U. 



