I 



THE BRITISH CONULARLE. 



species the author gave a complete list of the species known at the time with 

 tables of vertical distribution in the different countries, and also made the first 

 attempt at a natural classification. 



GENERAL MORPHOLOGY. 



(1) Form of the Shell. — The shell is always in the form of a straight four-sided 

 pyramid. The few cases among British species in which a slight curvature is seen, 

 are probably due to accident. The tapering of the shell is generally uniform, 

 though there are several exceptions in which the sides become nearly parallel 

 towards the aperture while converging more rapidly in the apical portion, e. <j. 

 G. subtil is (Plate IV, fig. 8). 



Fig. 1. — Diagram of Conularia. a. Aperture, b. Apertural lobes, c. Faces of the pynuuid. d. Marginal 

 groove, c. Transverse ridges. /. Facial groove. <j. Apex. 



(2) Cross- Section. — The section of the shell at right angles to the long axis varies 

 considerably. Very frequently deformation has taken place, but is not easy to 

 detect, as a square is converted to a rhomb, without any distortion in the shell 

 itself. Hence the observed cross-section is often misleading, though there are 

 certain characters in the ornamentation which throw light upon the natural form 

 (see " Ornamentation," p. 8). 



In the majority of cases the transverse section is a square in which the sides 

 are either straight lines as in C. quadrisulcata and G. hispida (PI. Ill, fig. 10), or 

 slightly convex curves as in G. crassa and C. globosa (PI. IV, fig. 5, and PI. Ill, 

 fig. 7 h). 



In a considerable number of cases the cross-section is in the form of a more or 

 less flattened rhomb, in which : 



