22 JOHAN KIÆR. M.-N. Kl. 



A number of other specimens show onl}' the broader and straighter 

 portion of the shell (text-fig. 4 a and b, plate III, figs. 4 and 5). It is of 

 interest to note that the angle of divergence varies somewhat, from about 

 2^ — ^0 Qj- ^0 T'l^e dimensions are often greater than those of the two 

 specimens given above, as will be seen from the following figures. 



Specimen ; Specimen 

 Cat. No. 13, ' Cat. No. 15, 

 XXVII. 227 i III, 6 



Specimen Specimen 



Cat. No. 15, I Cat. No. 13, 

 III, 4 ! XXVII, 497 



Total length 15 mm. 17 mm. 9 mm. | 18 mm. 



Breadth at the broadest and . . 2 „ 14» i-7 „ f.7 « 



Breadth at the narrowest end . r „ 0.8 „ 0.8 „ 0.6 „ 



Other specimens show more or less fragmentary initial portions (text- 

 fig. 4 e). I have not succeeded in observing the extreme apex in any of 

 my specimens. Some of them, — as for instance the specimen depicted 

 by me on plate III, fig. i, — may be assumed to be young individuals in 

 whom the initial portion is only developed, but the majority are doubtless 

 fragments of larger specimens. They are quite common in many layers 

 of the shales, and often in a bad state of preservation (pi. Ill, fig. 3). 



Sculpture: In some specimens we can see fine, indistinct, and some- 

 what irregular transverse lines which ma}- be assumed to be original. In 

 others we often see faint irregular oblique lines, but this can scarcely be 

 taken to be connected with the original sculpture of the shell. 



The composition of the shell: As a rule the shell has vanished. 

 In some specimens from the new excavation for a well just near the old 

 locality, however it is preserved. It is quite thin and black in colour. 

 Some specimens are also found in Sh-e/iiiel/a-Vimestone. 



Transverse section of the shell: In all the specimens preserved 

 in the shales the section is not the original one. The shell has been com- 

 pressed, although to a varying degree, as shown by text-fig. 4 f — g. For- 

 tunately one fragment was found in a sandy limestone at Tomten (text- 

 fig. 4 h). This specimen is plastically preserved, and shows the original 

 cross section.' The two axes of the latter are to one another as i : 1.5. 

 I therefore conclude that the Tømten form has a shell with such a section. 



Both in the last-named specimen and in the ordinary shale specimens 

 both sides of the shell appear to have been arched, and quite similar. 



Occurrence: Generally in the Hohnia shales at Tømten, both in 

 the old cutting and in the new excavation for a well in the neighbourhood. 



