112 



BRITISH BELEMNITES. 



forms are concerned. Only one specimen has yet been met Avitli corresponding in size to 

 the figures of D'Orbigny and Quenstedt already referred to. This is in the collection of 

 Mr. James Parker, from the Cowley clay pit at its deepest part, about 80 feet below the 

 Calcareous Grit. This specimen has a total length of 6-75 inches ; greatest breadth 65 ; 

 least 0-40 ; greatest depth 60 ; least 0-40 ; axis = 5'5 inches. Between this fine and 

 solitary specimen and very many examples 2? inches long, no intermediate magnitudes 

 have yet, near Oxford, been found ; the smallest specimens, like oat grains, are about half 

 an inch long, and then by decay of the laminae al>out the alveolar apex acquire the aspect 

 of the so-called ' Actinocamax' of Miller. 



Proportions. In young specimens the axis is about seven times as long as the greatest 

 post-alveolar breadth, and about ten times as long as the breadth at the alveolar apex : in 

 an old specimen, the axis is fourteen times as long as the alveolar breadth, and nine times 

 as long as the greatest post-alveolar breadth. 



It was with great pleasure that I received from the Oxford Clay of Eyebnry, near 

 Northamptonshire, a specimen found by Mr. Leeds (PI. XXVIII, fig. 68), which happily 

 fills up the blank in the history of the species, by a form of intermediate magnitude, not 

 elsewhere recognised. We are thus assured of the persistence of the hastate form in this 

 species through all stages of growth yet observed, from the very young to the apparently 

 full-grown individuals. 



Phragmocone. Very few indications of this part of the fossil have been as yet seen 

 by me. D'Orbigny, who had fine specimens at his disposal, figures the phragmocone of 

 one ('Terr. Jurassiques,' pi. viii, fig. 1) in the sheath, and represents it as having an angle 

 of about 1.5° (in the description it is said to be 11° to 18°), with chambers whose 

 diameter is only four times their depth. Quenstedt ('Cephal.,' pi, 29, fig, 8 a, 9) presents 

 the phragmocone of B. semihastatus rottmdus (regarded as a variety of B. hastatus by 

 D'Orbigny), with septal intervals equal to one fifth of the diameter, and an angle of 1 3°. 

 These may be regarded as good characters for discriminating between this specific group 

 and that of B. ari-pistilhm of Stonesfield. The septa are more nearly round than in the 

 figure of D^Orbigny. 



Localities. In Oxford Clay, Weymouth ; in the middle part of the clay north of the 

 town ; on the shore in the upper part of the clay ; and south of the town. Oxford, in 

 the lower or middle part of the clay, with Ammonites Duncani, at Summertown, one mile 

 to the north ; in the upper part of the clay at Cowley Field, half a mile to the south-east ; 

 and at Long Marston, in the upper part of the clay, one mile to the north-east {Phillips). 

 Eyebury, near Peterborough, in the lower part of the clay {Leeds). St. Ives [Walker). 

 Scarborough Castle Hill {Phillips). In Calcareous Grit, Scarborough {Bean). 



Observations. D'Orbigny collects under one title the two fossils to which Blainville 

 assigned the names of Belemnites hastatus and B. semihastatus. The differences between 

 them were far from clear in the earlier author's descriptions or figm-es. Quenstedt 



