6 THE BRITISH CONULARLE. 



sub-central, according to the position of this bend. In G. microscopica (PI. II, 

 figs. 6, 7), they are unusually deep and constant. Secondary facial grooves, 

 dividing again the half faces, are only seen in the early smooth forms. 



In three species the centres of the faces are marked by fine, internal, 

 longitudinal ridges, the internal septa of Lindstrom. 1 In British forms they are 

 in pairs in G. punctata (PI. I, figs. 10 a, 11) and G. aspersa (PI. I, figs. 5, G b), 

 and single in C. tenuis (PI. II, fig. 2). They appear to be fine, biconvex ridges 

 on the inner surface of the shell. As the result of compression, and owing to the 

 thinness of the shell, in the two latter species they are often seen as raised ridges 

 on the outer surface ; in C. aspersa these ridges are usually accompanied by a 

 black stain, probably indicating the position of some important anatomical 

 structure (PL I, figs. 6 h, 9 c). 



(5) Aperture and Apex of Shell. — The aperture of the shell is not commonly 

 preserved, though many perfect examples are known, especially among specimens 

 from ironstone concretions. Each face terminates in a roughly triangular lobe, 

 on which the general ornamentation of the face is continued. Generally these 

 lobes are short and rigid and bent down at right angles to the axis of the shell, 

 partially closing the aperture, as in G. quadrisulcata and C. sowerbyi (PL III, 

 fig. 6; PL V, fig. 8) ; but in G. aspersa they are long, and meet, forming an elevated 

 cone (PL I, fig. 5) ; in this species the shell is very thin, and the apertural lobes 

 were probably not rigid. 



In the greater number of specimens the delicate apical portion of the shell is 

 not preserved, but examples are found in some species where the pyramid tapers 

 to a fine point. It is generally difficult to make out whether this end was closed 

 or open ; but in one species there seems good evidence that the latter state 

 prevailed. G. tenuis is found in a good state of preservation in the hard, shaly 

 Calciferous Sandstone of Glencartholm, Dumfriesshire, and on slabs of this rock 

 examples are found in clusters, varying in number from two to as many as sixteen 

 (PL II, fig. 1). The size of the individuals of the cluster varies, some being quite 

 small and some full grown. They must have been connected with one another or with 

 some foreign body by their apices, which must therefore have been pierced during 

 some part of the life of the animal. I have found no trace of this fixed condition 

 in any other species, nor have I found any reference to it in published works, 

 except in a short article by Ruedemann,- entitled " Note on a Sessile Conularian." 

 He describes this form as a typical Conularian, in which the delicate pyramid base 

 is inserted in a chitinous cup, which by means of suction acted as a temporary 

 organ of attachment. The attachment in the case of G. tenuis can hardly have been 

 temporary, and from the size of the individuals must have been an adult character. 

 In a large number of species, instead of tapering to a fine point the pyramid is 



1 G. Lindstrom, ' Silur. Gastrop. Gotland,' p. 46. 



2 'American Geologist,' vol. xvii (181)6), p. 158. 



