■10 G. LINDSTRUM, ON TIIR SILURIAN GASTROPODA AND rXEROPODA OF GOTLAND. 



the tertiary formations. In still stronger terms than H;eckel, Neumayr in his 

 paper »Zur Kenntniss tier 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 Conulariai with the Pteropods and ho regards them rather as Gastropods nearly 

 allied to the palaeozoic Capulid;c '). But if we closer consider into this matter, there 

 appear points of connexion between the Conulariai as palaiozoic presumed Pteropoda 

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

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

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

 resemble eacli other in a Iiigh degree. There are also instances of a pyramidal shape 

 in the threesided shell of Cleodora lanceolata Rang or Cleodora pyramidata 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 la^vis; as for instance in Cleodora balantium Rang (Balan- 

 tium Childreni Adams p. p.) and others. Moreover, amongst the now living Pteropoda 

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

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

 dence in the exterior shape between species so Avidely apart in a chronological point 

 of view as the Silurian or palaeozoic 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 Capulida:-, the presence of two peculiar lon- 

 gitudinal septa on the inner surfaces of the shell of some Conuluriae, 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 Cleodorae and tlie Styliola^ are provided with quite similar septa. These 

 septa do not occur in all Conularia?, 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 Iiipirtng in his paper: »Dic Aptychen als Beweismittcl fiir die Dibrancliiatcnnaliir der 

 Ammonitenu in N. Jalirbueli fiir Miner, mid ficol. 1881, Bd 1 p. 87 insists that the Conulariae are no Ptero- 

 pods, hut rather to l)e considered as Cephalopoda, analogons to Endoceras. Of course the thinness of the shell 

 ill most of tiie ConulariiC cannot in itself be held as a very valid argument for their relation to the Pteropods, 

 l)ut taken in connexion with the characteristic ornamentation of its exterior, with the remarkable longitu- 

 dinal septa of the interior the aspect of the matter looks otherwise. The argument preferred that since the 

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

 when lliEUiNo published the statement given above, Conulariic as well as Hyolithes have been detected in 

 mesozoic 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 f|nestion where formed. The sami; mode of reasoning might some 

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

 strata between the palaeozoic and latest tertiary. The significance of liie size in the palreozoic and the recent 

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

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

 places the Couulariii^ amongst the Pteropoda, as well as Saltrii in his posthnnions Catalogue. Dana in the 

 iWanual of Geology makes the mistake to delineate the septum of Conularia with a siphoual opening. The 

 presence of one or more diaphragms in this shidi proves (juite as little their nature of Cephalopoda as the occur- 

 rence of diaphragms in true (iastropoda or even other groups of animals (Serpulne and others, Araplexus 

 amongst Corals) prove auythiiig for their Ijeing C'cphalopnda. 



