TURR1LITES. 61 



1. Turrilites tubkrculatus, Bosc. Plate XXV, figs. 1 to 4, and PL XXVI, figs. 15, 16. 



Turrilites tuberculatus, Bosc. Buff, da Deterville, Vers., t. 42, fig. 8. 



— — Sow. Min. Conch., t. 74. 



— — Mantell. Geol. of Sussex, t. 24, fig. 7. 



— D'Orb. Pal. Franc. Terr. Cret., t. 144, figs. 1, 2. 



— — Pictet and Roux. Foss. des Gres Vert de Geneve, t. 15, fig. 10. 



— varicos a, Bosc. I. c, p 190. 



— giganteus, Ilaan. Mon. Anim. et Goniat., p. 78. 



T. testa turritd, sinistrorsd ; anfractibus numerosis, extra convexis, tuberculato-spino.six .• 

 tuberculis 4-serialibus ,■ serie superiori, in medio anfractuum, tuberculis 20 distantibus, 

 maximis, spinosis ; seriebus tribus inferioribus prope suturam tubercidis parvis, numerosis, 

 approximatis ■■ ayigido spirali 16° — 20°. 



Shell turreted, with a spiral angle of 16° to 20°, sinistral : whorls numerous, rounded 

 externally, with one row of above 20 very large spinose tubercles near their middle, and 

 three rows of numerous small tubercles near their base, the lowest of which three rows is 

 concealed by the suture ; the tubercles of the middle row have a rounded base, those of 

 the three lower rows are elongated in a direction parallel to the suture, and are of the 

 same number in each row : upper and lower sides of the whorls ornamented with faint, 

 radiating ribs, corresponding to the tubercles of the lowest row : umbilicus narrow : 

 section of the whorls nearly rhomboidal, with the outer side convex : mouth somewhat 

 produced, and rising to a blunt point on the inner side of the whorl, and surrounded by a 

 wing-shaped expansion, with a nearly semicircular outline. 



The figures 1 and 4 represent the usual form of this species, with nearly twice as many 

 tubercles in the lower rows as there are in the upper one ; but specimens are often found 

 like fig. 3, with less difference between the different rows in the size and number of the 

 tubercles, and with the two lower rows of tubercles almost coalescing. I have seen no 

 specimen in which these two varieties are found in the same individual, as is represented 

 in M. D'Orbigny's fig. 1 ; but as the lobes of the septa of the two forms closely correspond, 

 we must presume that they belong to the same species. In very large individuals the 

 tubercles of the upper row are fewer in number, and proportionably larger. 



The lobes of the septa are much divided and branching ; the outer side of the whorl 

 holds half of the dorsal lobe, the dorsal saddle, and half of the superior lateral lobe, which 

 last has five principal branches ; the dorsal saddle is divided into two nearly equal parts, 

 and each of these is divided into two nearly equal branches (fig. 15). This is the character 

 by which T. tuberculatus is best distinguished from T. Gravesianus, which has the dorsal 

 saddle divided into two very unequal parts, only the upper of which is again divided. 



The larger specimens of Turrilites are never found perfect, so that their length must be 



10 



