ANIMAL TO ITS SHELL IN SOME FOSSIL CEPHALOPODA. 105 



At a point 29 mm. in advance of the small median saddle, the periphery is crossed by 

 an incised line which on the left side passes inward and backward for about 8 mm., 

 tlien passini? backward nearly parallel to, and at a distance of 8 mm., from the median 

 line of the perijAery until it meets the external saddle. Traces of a precisely similar 

 line can also be seen on the right side. This I believe to have also been part of tlie 

 anterior boundary of the annulus. 



Clymenia., Miinster. 

 CUjmeuia imdulata, Miinster. — The muscixlar impression in the genus Clymenia has been 

 best observed in an example of this species in the British Museum Collection (No. 81826). 

 It is from the Clymeuien-Kalk (Upper Devonian) of Scbiibelhammer, Bavaria (PI. 20. 

 figs. 13, 14). This specimen, the outer wdiorl of which is somewhat imperfect, has the 

 following dimensions : — Diameter of shell 48'5 mm. ; width of umbilicus 20'5 mm. ; 

 height of outer whorllG mm. ; greatest thickness of ditto 12 mm. Nearly one half of the 

 outer whorl is occupied by the body-chamber, its length, measured along the periphery, 

 being 65 mm. ; its anterior portion is flattened for a distance of nearly 20 mm., the width 

 of the flattened portion being 3 mm. It niay be remarked that in this genus the 

 siphuncle is on the inner side of the whorl, and is relatively much larger than in the rest 

 of the Ammonoidea. The internal cast of the posterior part of the body-chamber and 

 of two or three of the succeeding loculi is denuded of the test. The base of the body- 

 chamber is 12'5 mm. high and 10 mm. thick, the periphery here being quite rounded. 

 One side of the basal portion is w^ell-preserved, but tlie other is somewhat imperfect. 

 On the well-preserved side (fig. 13) a curved feebly-iucised line arises almost close to the 

 suture of the shell and at a distance of 2 mm. from the last sejitum ; j)assing backward 

 nearly parallel to the inner half of the lateral portion of the suture-line, it just clears 

 the most anterior poi'tion of the latter and then passes straight on to the periphery, 

 being at the centre of the latter about 2 mm. anterior to the last septum. It appears 

 to cross the periphery without iuterruj)tion, but unfortunately the line here is somewhat 

 obscured, and it is not impossible that the line here may be bent backward into a 

 very minute V-shaped sinus. 



Another feebly-incised line proceeds from the suture of the shell and passes backward 

 almost close to the last septum for some distance into the lateral lobe ; then turning 

 forward it meets the anterior line, already described, at the most anterior point of the 

 lateral portion of the suture-line. At a short distance from this junction and a little 

 nearer the periphery, the anterior line gives off a bi-anch which gradually recedes from 

 it and crosses the periphery about 1 mm. posterior to it. At the central portion of the 

 periphery this line, like the anterior one, is somewhat obscured, but appears to cross 

 the periphery without interruption, although it is not impossible that at the middle of 

 the periphery this line may have had a very small V-shaped bend forward. 



It would seem, therefore, that the shell-muscle occupied the space between tlie suture 

 of the shell and the outer side of the lateral lobe, and that the annulus extended from 



15* 



