THE CEPHALOPODA 189 



Alongside the typical Belemnoids of the Mesozoic runs 

 an allied stock (Phragmoteuthis, Trias ; Belemnoleuthis, 

 Upper Jurassic ; Conoteuthis, Lower Cretaceous), in which 

 the guard is a very thin investment of the phragmocone. 

 By reduction of the phragmocone and guard with re- 

 tention of the proostracum, this may have led to the 

 modern squid, Loligo. 



Short Bibliography. 



BARRANDE, J. Systeme Silurien de Boheme : vol. ii., 

 Cephalopodes (1865-70). 



BUCKMAN, S. S. (i) Yorkshire Type Ammonites, 

 2 vols. ( 1 909- 1 9) , continued as Type Ammonites (1919- ) ; 



(2) Pal. Soc., see below ; (3) numerous papers in Quart. 

 Journ. Geol. Soc. (1881-1918). 



CLARKE, J. M. The Protoconch olOrthoceras, American 

 Geologist, vol. xii. (1893). 



CRICK, G. C. (i) Muscular Attachment of Animal to 

 Shell in Ammonoidea, Trans. Linncvan Soc., vol. vii. 

 (1898) ; (2) On the Aperture of a Baculite, Proc. Malac. 

 Soc., vol. ii. (1896) ; (3) On the Proostracum of a Belem- 

 nite, the same ; (4) numerous papers in the same Proc., 

 and in Geol. Mag., etc. 



D'ORBIGNY, A. A. Paleontologie Fransaise. Terrains 

 Jurassiques, Cephalopodes, 2 vols. (1842-49); Terrains 

 Cretaces, Ceph. (1840). 



DOUVILLE, H. Ceratites de la Craie, Bull. Soc. Geol 

 France, vol. xviii. (1890) ; and many other papers in the 

 same periodical. 



HYATT, A. S. (i) Genesis of Arietidae, Smithsonian 

 Misc. Coll., No. 673 (1889); (2) Pseudoceratites of the 

 Cretaceous, U.S. Geol. Suyv., Monograph 44 (1903); 



(3) various papers in Proc, Boston Soc. Nat. Hist, (from 

 1875). 



