394 Dr. O. A. L. Morch on the Systematic Value of the 



branchiocardiac veins, the Cephalopoda must then be removed, 

 according to the septiserial teeth of the tongue, to the Tsenio- 

 glossata, the larvae of which [Macgillivrayidce) are not unlike the 

 Cephalopoda. This position would answer to that of Cetacea 

 being united by the Sirenians to Pachydermata. 



The pelagic Cephalopoda are certainly the most powerful and 

 ferocious of all Mollusca, like the Sharks and Cachalots among 

 Vertebrata; but in the same divisions are found large animals 

 living on small animals (e. g. the Whalebone-Whale and the 

 Squalus glacialis). The same is probably the case with the 

 largest of all Cephalopoda, Architeuthis dux, Stp. The two man- 

 dibles of the Cephalopoda are generally very powerful and very 

 conspicuous ; but their little value as a character for a class is 

 best seen by the two divisions of mandibulated Echinodermata 

 and the Helicea. The eyes offer the same differences as in other 

 parts of the animal kingdom, being small in the diurnal species 

 and larger in the nocturnal. The size of the lens cannot be 

 considered a character of perfection of the visual organs, because 

 the fishes would in such case have the most perfect eyes among 

 Vertebrata. Nautilus wants a lens, according to Prof. Keferstein. 

 The exterior form of Cephalopoda is a combination of the form 

 of the Fishes and Radiata*, depending on their manner of loco- 

 motion. Cirroteuthis has thus a striking resemblance to a Me- 

 dusa. The Cephalopoda seem to me not to have more just 

 claims to be considered a distinct class in relation to the other 

 Mollusca than Pteropoda or the Cetacea among Vertebrata. 

 They exhibit a remarkable analogy with the Plagiostomes in 

 their habits, in the male organ, the manner of depositing their 

 eggs, and in the yolk-bearing young. 



Subkingdom III. MOLLUSCA. 



Series I. MONOTOCARDIA. 



The heart with a single auricle. Copulation hetween two individuals. 



Class I. ANDROGYNA (Musivoglossata olim). 



All individuals alike in respect of the sexual organs, having the two 

 sexes united. Always provided with a receptaculum seminis (petio- 

 late hladder). Male organ retractile. Teeth of the tongue generally 

 multiserial. Predominantly mandibulated. 



PULMONATA. 



Geophila : Phyllovora, Agnathaf. 



IIygrophila: Planorbis, Physa, JAmncea, SipTionaria, Ancylus, 

 Auricula. 



* Owen, Proceedings of the Zool. Society, 1836, p. 19. 

 t Journal de Conchyliologic. July 1865. 



