106 ME. G. 0. CEICK OX THE MUSCULAR ATTACHMENT OF THE 



tlie outer side of the lateral lobe across the perijihery as a narrow band having its 

 greatest width at the centre of the periphery. 



Unfortunately, the opposite side of the body-chamber is not sufficiently well-preserved 

 to show the muscular impression. 



Near the anterior end of the body-chamber the internal cast exhibits a wide and 

 fairly deep groove, which crosses the lateral area in a curve which is concave forward, 

 and projects considerably forward near the periphery. The lateral portion of the 

 sroove is fully mm. wide, but shallow, while the portion near the periphery is 4 mm. 

 wide and deeper than the rest. The opposite side of the specimen is broken here, and 

 does not show the groove. This groove, however, seems to have nothing to do with the 

 muscular attachment of the animal, but is here mentioned for comparison with tlie 

 groove which has been depicted in some Ammonoids (e. g. Pinacoceras*) as the anterior 

 bonndarv of the muscle and of the annulus. 



GONIATITES. 



Gltphioceeas, Hyatt. 



Glyphioceras crenistria, J. Phillips, sp. — Among the Goniatites the form of the attach- 

 ment of the animal to its shell is well seen in an example t of this species from Bolland, 

 Yorkshire (PL 20. figs. 15, 16). It forms part of the British Museum Collection 

 (No. C. 5080). It is a Avell-preserved example, having the following dimensions: — 

 Diameter of shell 43 mm. ; width of umbilicus about 4*5 mm. ; height of outer whorl 

 21-5 mm.; thickness of ditto 27'5 mm. The body-chamber occupies five-sixths of the 

 outer whorl, and, being denuded of the test, its internal cast is well displayed. The 

 muscular attachment is so well preserved that it can be traced from the umbilicus on one 

 side across the whorl to the umbilicus on the other side. As seen in a lateral aspect 

 (fio". 15) the muscular scar is almost confined to the inner area of the whorl, and is 

 depressed (on the internal cast) a little below the sui'rounding surface. The most 

 anterior portion of its anterior boundary is a little more than 2 mm. in advance of the last 

 septum. Passing backward and outward, this boundary just crosses the umbilical margin 

 and reaches to within about 1 mm. of the septum, when, turning abruptly outward, it is 

 continued as a very fine raised line at this distance from the septum, until passing into 

 the lateral lobe, when it recedes very slightly from the suture-line. It crosses the lobe 

 in an obtuse point 3"75 mm. from the point of the lobe, and, then passing up the other 

 side of the lobe, it gradually approaches the suture-line and, just clearing the pointed 

 external saddle, passes into the external lobe at about 1 mm. from the septum (fig. 16), at 

 the same time separating into two very minutely -waved lines; at 5 mm. from the apex 



* Dr. E. V. Mojsisovics, ' Das Gebirge um Hallstatt," i. pi. xx. figs. 2 & 3 (^Pinacoceras insectum) ; pi. xx. 

 figs. 8 & 9 {P. liumilc). 



t This is the specimen from which the suture-liue figured in Cat. Eoss. Ceph. British Museum, pt. iii. p. 101, 

 fig. 76, was drawu. 



