284 Messrs. Foord and Crick on new and 



Nautilus obesus (see fig. 11), but it is distinguished by its 

 closer septa, the position of its siphuncle, its more slender 

 whorls, and narrower periphery. 



The specimens were all obtained in the Northamptonshire 

 Ironstone, and from most of them the shell has been dis- 

 solved away, leaving hollow spaces surrounding the casts. 



Horizon. Inferior Oolite. 



Locality. Duston, Northamptonshire. 



13. Nautilus clausus, d'Orbigny. 



1842. Nautilus clausus, d'Orbigny, Paldontologie Francaise, Terr. 



Jurass. vol. i. p. 158, pi. xxxiii. 

 1849. Nautilus clausus, d'Orbigny, Prodr. de Paleont. Stratigr. vol. i. 



p. 260. 

 1852. Nautilus clausus, Giebel, Fauna der Vorwelt, Band iii. Abth. i. 



p. 155. 

 1858. Nautilus claustts, Quenstedt, Der Jura, p. 350. 

 1858. Nautilus clausus, Chapuis, Nouv. Eecb. sur les Foss. des Terr. 



Secondares de la Province de Luxembourg (Acad. Roy. de Bel- 



gique, torn, xxxiii. des Mem.) pt. i. p. 14, pi. iii. fig. 1. 

 1800. Nautilus clausus, Wright. Quart. Joum. ( reol. Soc. vol. xvi. p. 13. 

 I860. Nautilus clausus, Ooquand, Synop. des Foss. Secondaires de la 



Charente, de la Cbarente-Inferieure, et de la Dordogne, p. 0. 

 1864. Nautilus clausus, Ebray, Etudes Geologiques sur le Bepartement 



de la Nievre, fasc. 13, 14, p. 270. 

 1868. Nautilus clausus, Dewalque, Prodrome d'une Description Geolo- 



gique de la Belgique, p. 352. 

 1873. Nautilus clausus, .Sharp, Quart. Journ. Geol. Soc. vol. xxix. 



p. 299. 

 ? 1878. Nau l //us clausus, Bayle, Explication de la Carte Geologique de 



la France, vol. iv., Atlas, pi. xxxvi. 

 1884. Nautilus clausus, Mallada, Boletin dela Comision del Mapa Geo- 



logico de Espana, vol. xi., Sinopsis de las Especies Fosiles de 



Espana, p. 228. 



Sp. char. Shell inflated, rapidly enlarging, somewhat 

 compressed on the sides, broad and flattened on the peri- 

 phery ; surface of test smooth or marked only with very fine 

 subregular lines of growth. Whorls completely involute, 

 widest in the region of the umbilicus, which is closed by a 

 shelly callus. Aperture much wider than high. Septa 

 slightly curved on the sides and forming a shallow sinus on 

 the periphery. Siphuncle a little below the centre. 



Remarks. This species bears some resemblance to Nautilus 

 subtruncatus, Morris and Lycett *, and it is also like N. 

 Baberi of the same authors ; it differs from the former in 

 its smooth test and from the latter in the same feature and 

 also in its closed umbilicus. 



* Mon. of the Mollusca from the Great Oolite, Pal. Soc. 1850, pt. i. 

 p. 10, pi. i. figs. 1,2. 



