42 Prof, de Notaris on Ginnania furcellata. 



to be the only one whose view refers the tubercle to the office of 

 a muscular fulcrum ; but he has fallen into an error in supposing 

 that it supported the pedicle or muscle of attachment*. 



Before concluding this brief account of the internal characters 

 of Productus, we must not overlook its mode of articulation, nor 

 the two crescent-shaped bodies often seen on its flat valve. By 

 some these crescent- shaped bodies are supposed to have been 

 produced by certain muscles ; on the other hand, there are many 

 who think that they have been the supports of the labial processes. 

 From the specimen of Productus comoides, which is figured by 

 Von Buch, exhibiting a pair of gyrated impressions f (the same 

 are even more obviously displayed on one of my specimens of 

 Productus gig aniens), I have no doubt that the mollusk of this 

 genus was furnished with spirally-folded labial appendages : I 

 hope to be able however to show clearly in my monograph, that 

 the crescent-shaped bodies did not support these appendages, 

 but, on the contrary, that they were produced by the ovaries. 

 Respecting the articulation of Productus, I have long been con- 

 vinced that it is effected without the presence of teeth or condyles : 

 by taking the tubercle or cardinal muscular support for an arti- 

 culating instrument, many palaeontologists have described the 

 Productuses as dentigerous. I have now examined a number of 

 species, and in every one the hinge plate of the flat valve exhibits 

 nothing but the cardinal muscular support-, while that of the 

 opposite valve presents a straight continuous surface, only occa- 

 sionally broken by a notch caused by the pressure of the part 

 just mentioned J. 



[To be continued.] 



VI. — On Ginnania furcellata. By Gius. de Notaris §. 



The celebrated Professor Meneghini, in his excellent work on 

 Mediterranean and Dalmatian Algse, has justly observed, that 

 the commonest species are often those whose peculiarities of in- 

 ternal structure are, in fact, least known, either because they are 

 supposed to have been already sufficiently illustrated, or because 

 they are regarded, I might almost say, with contempt. Of this 

 number, if I mistake not, is the Halymenia furcellata of Agardh, 

 a species common enough on the coasts of England and western 

 France and in some parts of the Mediterranean ; and although 



* Annates des Sciences Naturelles, tome xviii. 



f Ueber Productus oder Leptssna. 



J Certain so-called Productuses are known to be dentigerous, but these 

 will be hereafter shown to constitute another genus. 



§ Extracted from a paper entitled " Sopra alcune Alghe del mare Ligus- 

 tico." Communicated by the Rev. M. J. Berkeley. 



