Miscellaneous. 465 



On the Fecundation of the Crustacea. By M. Coste. 



In most of the species of Decapod Crustacea, the first two pairs of 

 abdoiiiiiml foot serve as appendages to tlie internal generative organs, 

 and form a sj)eeial apparatns, the function of wliich has not hitherto 

 been thoroughly known. Tlie Cray-fish preserved in the basins of 

 tlie College de France have allowed M. Gerbe to ascertain this func- 

 tion. During copulation, these two yaiTS of apj)endages are erected, 

 tending backwards and a little outwards. The posterior pair engages 

 its foliaceous extremity in the twisted channel presented by the an- 

 terior pair ; and the extremity of the deferent canal becoming evagi- 

 nated in the form of a penis, between the appendages thus united, 

 but moveable upon each other, pours out the seminal matter at their 

 base. As it is excreted, this matter flows slowly along the deep 

 furrow of the first appendages, and is deposited by them upon the 

 sternum of the female, where it becomes concreted, acquiring vermi- 

 cular forms. 



As the seminal matter of most Crustacea, and especially of the 

 common Cray-fish, is dense, and becomes rapidly solidified when in 

 contact with water, the horny channel through which it runs would 

 be easily obstructed, if the spoon-like extremity of the posterior piece 

 were not adai)ted to clear it by repeated forward movements at each 

 emission of semen. — Comptes liendus, March 1, 1858, p. 432. 



On the Dorsal Cavity of certain Ammonites. 

 By Professor Quenstedt. 



Notwithstanding the numerous investigations which have been 

 made upon the Ammonites, there still remain some points to be 

 explained with regard to them ; and until this has been done, no 

 precise determination can be effected of a great number of species. 

 M. Quenstedt had long since observed in many casts, along the 

 siphon, a cord, without septa, which is easily detached. His obser- 

 vations upon the A. Truellei, D'Orb., from the lower oolite of 

 Montiers, led him to the following results. Large fraaiments of this 

 Ammonite show that the ferruginous oolite has penetrated into the 

 dorsal cord, which would only be possible if this cavity were not 

 closed. If the cord be broken, a second shell is formed beneath it, 

 and below this the siphon which traverses the septa. 



Neither D'Orbigny nor Oppel have perceived this fact. It is true 

 that it is ascertained with difiiculty in small individuals : thus no 

 trace of an a})erture is seen in a young A. pnstidatus from Bellay ; 

 whilst an adult shell of the same species, derived from the Ornater 

 Than of Gammelshausen, presents a pyritous crest, which is easily 

 detached, and which proves its analogy with A. Truellei. The largest 

 dorsal cavity observed by Quenstedt was presented by a fragment of 

 an Ammonite from the brown upper Jura of Rathshausen, to which 

 he has given, in consequence of this organization, the name of A. 

 dorsocavutns. This Ammonite has the same spiral lines and the 

 same high and compressed mouth as the A. Truellei, but it has on 



Ann. cY Mag. N. Hist. Ser. 3. Vol. i. 30 



