EXPLANATION OF PLATE L 



Fig. 



1. Belemnites acutus. 



d. Dorsal aspect. 



/. Lateral aspect. The groove here seen is seldom so distinct. 



V. Ventral aspect. 



s. Section from the back to the front. The alveolus is excentric, and is ex- 

 panded by compression : v, ventral ; d, dorsal portion. 

 J, J. Young specimens, showing their elongate form. 



a. Apicial portion of the guard, showing striation, which is not usual, and is refer- 

 able to decay. 



s". Transverse section at the apex of the alveolus, showing the greater breadth of 

 the ventral region, which, however, is here somewhat broader than usual. 



2. Belemnites penicillatus. 



d. Dorsal aspect. 

 l',l",r". Lateral aspect; /' and /"' show lateral grooves and terminal striae. 

 These grooves are seldom quite untraceable, though they do not appear in 

 I", a younger specimen, which, however, is more striated, and at the apex 

 umbilicate ; these appearances in /" are due to partial decay. 



V. Ventral aspect. 



s. Longitudinal section, showing the straight-sided central alveolus. 



s' Transverse section, showing the elliptical section of the alveolus and the 

 flattened sides of the guard. 



s" Transverse section of the guard, showing the central axis. 



3. Belemnites infundibulum. 



d', d", d'". Dorsal aspect, showing the usual striae, which are enlarged in a. 

 I', l". Lateral aspect, showing the usual inflexion of the apex. 

 V. Ventral aspect, on which the striae are usually shorter. These striae are 



not due to decay, but to original formation, 

 s" Transverse section, nearly round, or subquadrate, or a little oval, accord- 

 ing to the specimen and the place of the section. 

 a. Enlarged striae. 



