1.2 WIIT1SH FOSSILS. 



So with regard to the acetabular hooks and beaks : that such slruc- 

 tures appertained to Belemnoteuthis was proved by Pearce and Cun- 

 nington and by Professor Owen ; but, at present, I am aware of no 

 direct evidence of their existence in Belemnites. 



These lacunas in our knowledge of one of the most important of extinct 

 forms of life are filled up by the specimens described in the present 

 Memoir, which demonstrate the accuracy of Dr. Buckland's view of the 

 nature of the Lyme Regis fossils figured in his Plates 44' and 44"; and 

 furthermore, prove that at least three types of structure of the pro- 

 ostracum must be distinguished among the Bclemnitidce, 



Some time ago, my friend Mr. Day of Charmouth was good enough 

 to direct my attention to a number of remarkable specimens of Belem- 

 nitida; obtained from the Lias in his neighbourhood, and noAv either in 

 his own possession, or in that of the Rev. Mr. Montefiore and Mr. 

 Henry Norri's, gentlemen to whom I am greatly indebted for the 

 readiness with which they have entrusted valuable and important 

 fossils to me for examination and description. 



The most complete Belenmite in existence, to my knowledge, is 

 that .specimen, the property of the Rev. Mr. Montefiore, which is 

 represented in Plate I., fig. 1. Mr. Day informs me that it was 

 obtained from the Ammonites obtusus zone of the Lower Lias near 

 Charmouth. 



In this remarkable fossil not only are the guard, phragmocoue, and 

 pro-ostracum preserved, but the general contour of the body is shown, 

 the beak is in its place, and irregular lines of hooks indicate the 

 position and extent of the arms. 



The length of the whole animal, from the summit of the beak to the 

 apex of the guard, is 12^ in., Avhile its greatest breadth does not exceed 

 1^ inches. The arms, as indicated by the lines of hooks, cannot be 

 traced for a distance of more than 1^ in. from the beak, and they 

 diverge from one another, so as to include a triangular space, the 

 broad base of Avhich is superior, while its apex is close to the beaks. 



The internal shell is 11 '8 inches long, and consists of guard, phrag- 

 mocoue and pro-ostracum. The guard and the phragmocoue occupy 

 rather less than the half of the whole shell (5*5 in. about). The guard, 

 about 0*3 in. thick in the middle, and nearly circular in section, remains 

 of about the same diameter for l^iu., widening, above, into the alveolus 

 for the phragmocone, while, below, it tapers to the apex. The inferior 

 narrowing commences at about half an inch from the apex, which is 

 marked by five indistinct, short, longitudinal grooves. Superiorly, 

 the guard spreads out over the phragmocoue, becoming gradually 

 thinner, and ceasing to be traceable, as guard, at the point (d'j, about 

 2f in. from the apex. 



The guard is broken at the points b smd c ; at b the surfaces corre- 

 spond perfectly, but at c there is a slight loss of substance, so that the 

 portion of the guard, a, c, may not be in quite its natural position 

 relatively to the rest. I am inclined to suspect that there has been some 

 slight shifting of position at this point, from the circumstance that the 

 curved contour of the right side of the guard is somewhat more convex 

 than that of the left side, while the whole guard is slightly flattened 

 in the plane of the surface of the matrix. The right contour should 

 therefore be ventral, and the left dorsal. But there can be hardly any 

 doubt that the upper face of the body of the specimen is the dorsal 

 aspect, so that it Avould appear that the guard, where broken at c, has 

 undergone a certain twist upon its axis. 



The primary chamber of the phragmocone probably lies in the guard 

 about the point indicated by the letter x. For the two lateral margins 



