'I o G. LINDSTRÖM, ON THE SILURIAN GASTROPODA AND PTKROPODA OF GOTLAND. 



the tertiary formations. In still stronger terms than HiECKEL, Neumayr in his 

 paper »Zur Kenntniss der Fauna des untersten Lias in den Nordalpen», Abhandlungen 

 der K. K. Geologischen Reichsanstalt Bd vii Heft. 5 p. 18, also objects to the affinity 

 of the Conulariaj with the Pteropods and he regards them rather as Gastropods nearly 

 allied to the pala30zoic Capulida3 ^). But if we closer consider into this matter, there 

 appear points of connexion between the Conulariaa as palajozoic presumed Pteropoda 

 and the recent ones, which make it most likely that the questionable fossils really are 

 Pteropods. First, as to the exteriör shape, it seems very difficult to deny that the 

 palajozoic Hyolithes and several of the recent, as for instance Cleodora australis Rang 

 resemble each other in a high degree, There are also instances of a pyramidal shape 

 in the threesided shell of Cleodora lanceolata Rang or Cleodora pyraraidata and several 

 others, Cleodora Deluciana forming an irregular sixsided pyramid thus making an 

 approach to the foursided shell of Conularia. As to the peculiar transverse ornamen- 

 tation of the last mentioned genus there are several instances of close resemblance to 

 what obtains in Conularia la3vis; as for instance in Cleodora balantium Rang (Balan- 

 tium Childreni Adams p. p.) and others. Moreover, araongst the noAv living Pteropoda 

 there is a sufficiently large araount of widely different forms, more so than in any 

 other group of the mollusca, that it is almost unnecessary to talk about close correspon- 

 dence in the exteriör shape between species so widely apart in a chronological point 

 of view as the Silurian or palasozoic and the recent ones. 



If not the nature of the shell in Conularia did exclude all thought of their 

 being Gastropoda allied to the thick-shelled Capulida3, the presence of two peculiar lon- 

 gitudinal septa on the inner surfaces of the shell of some Conularia3, as for instance 

 C. bilineata and C. aspersa at once makes such a comparison impossible. Their pre- 

 sence, on the contrary, is a homology with the recent Pteropoda, amongst which se- 

 veral of the Cleodorte and the Styliola3 are provided with quite similar septa. These 

 septa do not occur in all Conulariaj, but are represented in many by one or more 

 median, ingoing folds. When more specific forms shall have been found and there is more 



') Lately also Ihering in his paper: »Die Apt^^chen als Beweisinittel fiir die Dibranchiatennatur der 

 Ammoniten» in N. Jahrbuch fiir Miner, nncl Geol. 1881, Bd 1 p. 87 insists that the Conularite are no Ptero- 

 pods, but rather to be considered as Cephalopoda, analogous to Endoceras. Of course the thinness of the shell 

 in tnost of the Conularioe cannot in itself be held as a very valid argument for their relation to the Pteropods, 

 but taken in connexion with the oharacteristic ornamentation of its exteriör, with the remarkable longitu- 

 diiial septa of the interiör the aspect of the matter looks otherwise. The argument proferred that since the 

 Palaeozoic period no Pteropoda have been found before the Tertiary age is of no value. Since the year 1881, 

 when lilEiiiNG published the statement given above, Conularire as well as Hyolithes have been detectcd in 

 raesozoic formations and moreover the circumstance of a fossil form not having been found docs not imply 

 that it never did exist when the strata in question where formed. The same mode of reasoning might some 

 time ago have been as well applied for instance to Chiton, of which then no speeimens were known in the 

 strata between tho palicozoic and latest tertiary. The significance of the size in the palpeozoic and the recent 

 ones is not to be taxed as high as Ihering and his followers think. Nor can I find on what grounds Ihering 

 enumerates Hall and Salter amongst the supporters of his views. The former in his latest works at least 

 places the Conularife amongst the Pteropoda, as well as Salter in his postiiumous Catalogue. Dana in the 

 Manual of Geology makes the mistake to delineate the septum of Conularia with a siphonal opening. The 

 presence of one or more diaphragms in this shell proves quite as little their nature of Cephalopoda as the occur- 

 rence of diaphragms in true Gastropoda or even other groups of animals (Serpnlfe and others, Amplexus 

 araongst Corals) prove anything for their being Cephalopoda. 



