WOODWARD — HIPPURITIDiE. 



61 



EXPLANATION OF PLATES IIL IV. V. 

 Plate III. 

 Fig. 1. Hippurites Loftusi, n. sp., \ natural size. 

 Fig. 2. A small portion of the upper valve, natural size. 

 Fig. 3. Transverse section of the lower valve, reduced. 

 Fig. 4. Interior of the upper valve, natural size. 



/, m, n. Inflections of the outer shell-wall. 



d. Outer shell-wall, with tubular structure. 



e. Inner layer of shell, with laminated structure. 

 t, t'. Teeth, or dental processes, of upper valve. 

 u. Umbonal cavity. 



c, Ligamental pit. 



s, s. Portions of the longitudinal ridges (inflections) of the lower 

 valve, broken off and remaining adherent to the upper valve. 

 The arrows indicate the supposed direction of the alimentary 

 canal and branchial currents. 



Plate IV. 

 Fig. 1. RadioHtes cyhndraceus, Desmoulins ; upper half of a longitudinal section, 

 in the cabinet of Mr. Sharpe. 



a, a'. Adductor processes of upper valve. 



b, b. Superficial layer of shell, rarely preserved. 



d, d. Principal, or cellular, layer of shell. 



e, e. Internal, or subnacreous, layer, replaced by spar. 



Fig. 2. Hippurites cornu-vaccinum, Bronn ; reduced. Transverse section of the 

 lower valve : from a specimen wanting the outer shell-wall ; and Fig. 3. 

 Section of the same specimen, lower down. 



I, m, n. Inflections of the outer shell-wall {d). 

 e. Inner layer, with finely laminated structure. 

 a. Position of anterior adductor. 

 a. Posterior adductor-process. 

 t, t'. Dental processes of upper valve. 

 Fig. 4. Hippurites corrugatus, n. sp. Transverse section of lower valve ; the in- 

 terior obscured by crystallization. 

 Fig. 5. Hippurites colliciatus, n. sp. Transverse section of lower valve ; ty t\ den- 

 tal pits. 

 Fig. 6. Hippurites vesiculosus, n. sp. Transverse section of lower valve ; the in- 

 terior partly metamorphosed. 

 N.B. The letters in figs. 4, 5, & 6 have the same meaning as in figs. 2 & 3. 



Plate V. 

 Fig. 1. Radiolites Mortoni, il/aw^e^/ ; reduced. A considerable portion of a lower 

 valve, seen from below. In the collection of Matthew Wright, Esq., of 

 Stoke Newington. 



<r, X, X. Surfaces from which other individuals have been detached. 

 V, V. " Vascular " markings on the rim of the shell. 

 Fig. 2. Internal mould (of the same specimen) composed of hard chalk, represent- 

 ing some of the water-chambers of the original shell, perforated by 

 Cliona. (See fig. 1.) 



r, r. Joints produced by the decomposition of the septa. 

 a, a'. Furrows produced by the adductor-ridges. 

 t, if. Furrows produced by the dental ridges. 

 (These letters refer to both figures.) 

 Fig. 3. Radiolites acutus, D'Orb. Interior of an upper valve, presented to the 

 British Museum by S. P. Pratt, Esq. The inner shell-layer with its pro- 

 cesses is entirely wanting ; I, the ligamental inflection, showing that the 

 umbo was marginal in the young shell. 

 Fig. 4. Radiolites Mantelli, n. sp. From the Upper Greensand of Cap la Heve. 

 Fragments consisting of portions of two lower valves, adherent. 

 i. Inner surface, wanting the inner layer. 

 I. Ligamental line. 

 e. External surface. 



