^fisceUa neous. 217 



be no longer present evin in the embryos, then we shall be able to 

 affirm that SeropJiix is u fjood genvis, because it will be quite distinct 

 from i^ijntinathus. At ]>resent we cannot (juite say that, as is proved 

 by the uncertainty which i>revail.s in the classification of certain spe- 

 cies : thus, tor example, Kaup places the iNV/VY)/;fs with rudimentary 

 tail in the genus yerophis. while Kafinesque and Bonaparte refer 

 them to the genus >SifU(jii(itfii(!<. 



" In the same manner the tertiary Cdhimostonui , in losing the 

 caudal fin, gave rise to the existing J/qq'ocampiis. in which the 

 caudal fin is only present in the embryo. 



" It is extremely probable that the caudal fin, before disappearing 

 from the adults, passes through the rudimentary state, as is the case 

 in the species of Xirojifiis cited above. No Hippocampus is yet 

 known presenting this degree of conformation ; but one may enter- 

 tain the expectation of discovering, either in the present seas or in 

 the postcocene formations, Ilippocuupi possessing in the adult con- 

 dition a rudimentary caudal. 



" With fishes the caudal is a powerful organ of locomotion. In 

 this resi)ect Uipiwampux is an exception, in that it effects its move- 

 ments principally by means of the dorsal. To it a caudal would be 

 almost useless ; and if that fin existed in the Calamostomes. perhaps 

 the reason was that it was inherited from other fishes. In the Hip- 

 pocampi it has been subjected to tliat law which condemns useless 

 organs first to become rudimentary and then atrophied in the 

 adults, and at last to disappear even in the embryo. The existing 

 Hippocampti are found precisely in the second of these three 

 phases." 



The paper of M. Canestrini concludes with a descriptive and ana- 

 lytical catalogue of the Lophobranchs of the Adriatic, comprising 12 

 species, distributed into 4 genera : — Hippocampus, 2 species ; ^'t- 

 phonostomus, 2 ; Sj/nf/naihus, (J, of which one(^'. tienionotus) is new ; 

 and Xerophis, 2. He rectifies numerous errors of synonymy com- 

 mitted by various authors, in particular by Bonaparte, whose 28 

 species of Lophobranchs ought to be reduced to 19. — Bibliotheque 

 Universelle, Archives des Sciences Physiques et NatnrelJes, Julv 15, 

 1871, pp. 355-358. 



On a new Organ of Innervation, and on the Origin of the Nerves of 

 Special Sensibilit)/ in the Aquatic PuJmonate Gasteropoda. By 

 M. Lacaze-Duthiers. 



In a former memoir I made known to the Academy a constant 

 and important relation Avhich exists between the organ of hearing 

 and the posterior nervous centres of the Gasterojjoda. Now, by the 

 investigation of nervous centres by means of histological preparations 

 intended to allow the nerves to be traced to their true and real 

 origins, I have been led to the knowledge of new facts of great 

 value for the knowledge of the relations and morphological com- 

 parisons. 



I believe that no one has yet indicated the existence in the sub- 

 Ann.& Mag. N. Hist. Ser. 4. Vol. Yin. 16 



