188 GASTEROPODA OF THE INFERIOR OOLITE. 



subconcave, sutural sulcus wide. The ornaments undergo considerable modi- 

 fication. Apical whorls unknown. Towards the middle of the spire the posterior 

 margin of each whorl carries a single row of roundish tubercles, below which is a 

 slight constriction, and then a convex zone made up of undulating spirals 

 decussating with short costos. In the anterior whorls a considerable change takes 

 place ; the whorls become concave, and instead of costse a single row of tubercles 

 occurs at each extremity, the spiral ornaments remaining the same. 



The body- whorl is relatively small, angular, and with a base which is depressed 

 and slightly excavated towards the centre. Aperture restricted anteriorly, sub- 

 oblong, columella short, outer lip slightly constricted. 



Relations and Distribution. — This is the most cylindrical of the several forms 

 described from the Inferior Oolite. It also differs considerably in the details of 

 ornamentation from C. Bajocensis. In other respects it must be regarded as 

 closely approximating to that species. When comparing it with species from the 

 Lias of Sicily it seems to resemble Cerithinella elega.ns, Gemm. (op. cit., p. 285, 

 pi. 23, fig. 34). Fig. 4 a represents the type-specimen obtained by Mr. Brodie 

 from the Leckhampton Freestones. Fig. 4 b represents either a variety, or the 

 earlier stage before the whorls become concave ; it was collected by Lycett from 

 the Inferior Oolite of Nailsworth. 



Fig. 5 represents the anterior whorls of a larger shell, somewhat modified by 

 mineralization from the Murchisonse-zone of Stoford. This last may represent 

 the maturer condition of C. Brodiei ; or, what is more probable, of C. Bajocensis, 

 var. drosera. 



Pseudalaria, genus novum. 



Testa subelongatd, conicd, acuta. Anfractibus spiraliter striatis, in medio vel sub 

 medio carinatis, carinis ssepe crenulatis ; ultimo anfractu bicarinato. Aperturd 

 quadratd, antice et postice subcanaliculatd ; labro dextro sinuato. 



The above generic diagnosis is practically that given by Deslongchamps in 

 describing Turritella unicarinata (vol. cit., p. 151, pi. xi, fig. 68), said to occur in 

 the Oxford Clay of Dives. Turritella Guerrei, Heb. and Desk (op. cit., p. 46, 

 pi. vi, fig. 6), from the Callovianof Montreuil-Bellay, is a somewhat narrower form. 

 Cossmann (op. cit., p. 229, pi. v, fig. 15) describes a still narrower variety of T. 

 Guerrei from the Bathonian of Le "Wast. 



The latter author observes that T. Guerrei might almost as well be an Alaria 

 as a Turritella, since the double keel reminds us so much of the former, though 

 the form of the aperture removes it completely from Alaria. He suggests a 

 change of genus. Undoubtedly the spire has a remarkable resemblance to some 



