MM. Fuord and Crick — On Nautilus elegans, Shy. 549 



Nautilus elegantoides, d'Orbigny. 



1840. Nautilus elegantoides, d'Orbigny, Paleontologie Franchise, Terrains Cietaces, 

 tome i. p. 89. 



Sp. Char. — This species is briefly described by d'Orbigny (Joe. cit.) 

 in the following paragraph : — " II parait done constant, d'apres les 

 observations des geologues et d'apres mes observations personelles, 

 que le Nautilus elegans est special aux couches des craies tufau; car, 

 tons les fragmens que j'ai recueillis dans le gres vert de la Normandie 

 (Vaches noires), me portent a croire qu'il y existe encoi'e une autre 

 espece voisine de Y elegans, mais bien plus etroite, et a. siphon plus 

 median, que j'ai nominee Nautilus elegantoides, mais je ne la possede 

 pas assez complete pour la caracteriser nettement." 



Remarks. — As no mention is made of this species by d'Orbigny in 

 his ' Prodrome ' or elsewhere, it may be assumed that he never 

 succeeded in obtaining such material as would have enabled him to 

 describe the species completely. There is, however, a specimen in 

 the British Museum (No. 37001) which possesses all the characters 

 essential for the diagnosis of the species, which may thus be 

 described : — Shell somewhat inflated, sides and periphery rather 

 flattened, thus giving a squarish form to the whorls in section ; 

 widest part of the whorls in the umbilical region. Umbilicus open, 

 of moderate size. Septa moderately distant ; sutures considerably 



Fig. 2. 



Nautilus elegantoides. — a, lateral view of a very imperfect specimen, showing the 

 form of the sutures; b, front view, showing the position of the siphuncle. 

 Drawn from a specimen in the British Museum. One-third natural size. 



curved backwards on the sides of the shell, and forming a conspicuous 

 sinus on the periphery. Siphuncle considerably below the centre of 

 the septa. Ornaments (seen only on the cast) consisting of strong, 

 prominent, transverse ribs, which often separate into bundles of 



