INVERTEBRATE PALAEONTOLOGY. 503 



generic characters, by the fact that Miller mentions in his specific descrip- 

 tion the presence of "branching impressions of blood-vessels," one of the 

 most marked characters of Belemnitella, and one never seen in Belemnites. 

 From these facts, it seems almost certain that Belemnitdla is a synonym of 

 Actinocamax, Miller, which has priority of date over Belemnitella. Miller's 

 name, however, has been generally rejected, because — not perceiving the 

 condition of his type — he did not understand its true characters. This, how- 

 ever, ought not, I should think, to set aside the claims of his name for the 

 genus, if there is no room for the least doubt in regard to the type-species 

 really belonging to the same genus as d'Orbigny's ; because, as every one 

 knows, a large proportion of the generic names now in general use, proposed 

 by the early naturalists, might in the same way, be set aside to give place 

 to later names published by authors having far more accurate knowledge of 

 the real characters of the genera named than the original founders of the 

 same. 



For the reasons above stated, I should not hesitate to retain the name 

 Actinocamax for this genus, were it not for the fact that, according to Herr- 

 mannsen, Linck had, as far back as 1807, proposed the name Atractites for 

 a type identical with Miller's Actinocamax. This, therefore, complicates the 

 matter, and, until these questions can all be cleared up, I have preferred, for 

 the present, to follow those who use d'Orbigny's name Belemnitella for this 

 genus, especially as it is still an open question whether Linck's work can 

 properly be regarded as a published document, since it is said that only two 

 or three copies of it were distributed before the destruction of the whole 

 edition by fire. 



This genus appears to be entirely confined to the horizon of the true 

 Chalk and the Upper Greensand of English geologists, and has an almost 

 world-wide geographical range, wherever beds of these horizons occur. 

 Like Belemnites, these mollusks seem to have been gregarious in their habits ; 

 great numbers of their guards being often found together in the same beds. 

 At some localities in New Jersey, I have seen thousands of the guards of 

 the common species B. mucronata lying about the Greensand Marl pits, 

 mingled with the marl that had been thrown out of the same. 



