ANIMAL TO ITS SHELL IN SOME FOSSIL CEPHALOPODA. 81 



20 mm., it is then at about 58 mm. from the last septum ; then with a broad curve it 

 turns backward until it is about 40 mm. from its commencement, when it appears to 

 rapidly die out. Although the impressions of these boundaries may perhaps be more 

 properly termed grooves, their form and position agree so well with what I have 

 observed in somewhat similar forms that I think there can be no doubt as to their 

 nature. I have not been able to observe any trace of the annulus in this example. 



Mackoscaphites, Meek. 

 Ifacroscophites fjigos, J. de C. Sowerby, sp. — In the genus Ilacroscaphites what 1 

 regard as the anterior boundary of the muscular scar has been observed in an example 

 of Ilacroscaphites gigas, J. de C. Sowerby, sp., in the British Museum Collection 

 (No. 32008). The specimen is stated to be from the Lower Greensand of the Isle of Wight, 

 but its matrix and state of preservation suggest rather the Kentish Rag (Lower Greensand) 

 in the neighbourhood of Maidstone (PI. 17. figs. 17, 18, 19). It is a much-compressed 

 internal cast ; the greatest diameter of its sej)tate jjortion is 180 mm. ; the length of its 

 body-chamber measured along the centre of the periphery and over the coarse ribs is 

 350 mm., the height of the base of the body-chamber is 68 mm., the thickness (including 

 the ribs) being reduced by compression to 22'5 mm. On the right side, at about 15 mm. 

 above the most anterior part of the last septum and 20 mm. irom the inner margin of 

 the whorl when viewed laterally, a very fine incised line arises and passes thence as a 

 flat arc forward and towards the inner margin, which it crosses at about 45 mm. in 

 front of tlie last septum ; it then curves backward and comes to within about 10 mm. of 

 the septum, w^here it is in the middle line of the compressed and somewhat distorted 

 dorsal area. From this point another line, making an acute angle with the line just 

 described, j)asses forward and outw^ard for rather more than 30 mm., when it curves 

 outward still more and then disappears. These two curved lines we take to be the 

 anterior boundary of the right and left muscular scars respectively ; no traces of the 

 annulus have been observed in this example. The material of this natural internal 

 cast is very coarse, and the specimen is so much crushed that the very faint lines bounding 

 the muscular scars can only be followed with difficulty ; the boundary is preserved partly 

 as an incised line and partly as a line of colour. 



ScAPHiTES, Parkinson. 



Scctphites biuodosus, A. Roemer. — The muscular impression can be traced in an 

 example of this species contained in the British Museum Collection (No. C. 5182). It is 

 from the Lower Senonian (Granulaten-Kreide) of Broitzen, near Brunswdck. The specimen 

 is a fairly well-preserved, but somewhat distorted internal cast. Its greatest length is 

 43 mm., and the greatest diameter of the septate portion is 26-5 mm. (PI. 17. figs. 20, 21). 

 At the posterior end of the body-chamber the whorl is 13'5 mm. higli and 10"5 mm. thick 

 (excluding the tubercles). The whorl is somew'hat crushed obliquely, so that its sloping- 

 inner area is much more clearly seen on one (the left) side. On this side a feebly-incised 

 (partly double) line arises almost close to the last septum, and at a distance of 5 mm. 



12* 



