294 J. Starkie Gardnei — 0?i the Qault Aporrhctidce. 



History; — Described by Forbes as a Pteroceras in 1845 in the 

 Quart. Journ. of the Geol. Soc. vol. i. p. 851, pi. iv. fig. 6; referred to 

 by Fitton in vol. iii. as occurring in bed 5a of the " Cracker nodules ; " 

 and figured by Mantell in the Geology of the Isle of Wight. 1847, 

 as Pt. retusa. The references to Pt. retusu from Atherfield, in 

 other works, should be read as A. Moreausiana. The original speci- 

 men figured by Forbes is in the Museum of the Geological Society, 

 it is remarkable for the great prominence of the tubercles on the 

 carinas. 



Distribution. — Atherfield ; not hitherto noticed on the Continent. 



Apporhais histochila, 1 Gardner. PI. VII. Figs. 5 and 6. 



Description. — Shell apparently thinner than that of the last species, 

 but having the same general form. It is bicarinated and finely stri- 

 ated, the front part of the shell is larger than that of A. Moreausiana, 

 and has more and seemingly better defined strips. The spire is 

 depressed, with rounded whorls. The stria? are arranged three or 

 four on the region above the posterior keel, four between the keels, 

 eight or nine anterior to them. The keels are prolonged into cligita- 

 tions, which sustain or strengthen a broad expanded wing, continued 

 to the apex of the spire ; of these digits the more anterior is very 

 straight and projected downward, the second is curved upward. 

 Some of the stria? above the posterior keel of the body -whorl are 

 continued on the wing, and follow the curves of the adjacent digit. 

 There is, probably, a posterior canal of the same size, and recurved in 

 the same manner as in A. Moreausiana. The anterior canal is not 

 very distinct on the specimen figured, but it seems accompanied by 

 a continuation of the expanded wing to near its end. There is the 

 characteristic sinus between the anterior canal and the front digit, 

 the margin of the wing being otherwise entire. 



This shell is very like A. Moreausiana, but the shape of the wing 

 with its entire margin, the rounded instead of angular whorls of the 

 spire, and the downward and straight anterior digit, combine to give 

 it a distinct aspect. The body-whorl is larger in proportion than it is 

 in the two species just described, and this character might seem to 

 identify the numerous casts that are found in the Upper Greensand and 

 Gault. It will be, at all events, safe to consider casts resembling this 

 shell, and found on the same horizon, to belong to this species, instead 

 of to A. Fittoni or A. Moreausiana, which characterize the Lower 

 Greensand. It is distinguished, in common with the two last, from 

 A. retusa by its elongated form, the less relative pi'ominence of the 

 anterior keel, and the number of striae. The casts from Cambridge 

 agree with this in form and in the number of striae below the keels. 



History. — This species has been variously labelled in different 

 museums — retusa, Fittoni, etc. A good specimen in the Geological 

 Society's Museum is labelled Pt. Bochatiana, D'Orb., by H. de la 

 Beche, but a reference to D'Orbigny's Prodrome suffices to show that 

 this is an error. 



Distribution. — Found in the Upper Greensand of Devizes, Lyme 

 1 From larbs webbed, and x«A.oj a lip. 



