82 MK. G. C. CRICK ON THE MUSCULAR ATTACHMENT OF THE 



from the inner edge of tlie Avliorl ; passing fovAvard in a broad, flattened, forwavdly- 

 convex cui've, it graduall}^ approaches and finally crosses the inner edge of the whorl at 

 about 7*5 mm. in front of the last septum. Passing on to the dorsal (or concave) 

 portion of the whorl, it turns backward, and in a rather broad forwardly-convex curve 

 nearly reaches the centre of this area, where it appears to be joined by the corresponding 

 impression on the opposite side. The boundary of the impression on the opposite side 

 is not quite so distinct, and on the sloping inner area of the whorl it appears to be a 

 little nearer the inner edge of tlie whorl than on the opposite side, but this is doubtless 

 due in great measure to the oblique crushing to which the specimen has been subjected. 

 At the base of the body-chamber it is only 2-75 mm. from the inner edge of the whorl; 

 passing forward it gradually approaches and finally crosses the same at about 7'5 mm. 

 in advance of the last septum. I'assing thence in a forwardly-convex carve, it joins its 

 fellow at about the centre of the dorsal surface of the whorl. 



The lines here described are probably the boundaries of the muscular scars. I have 

 not seen any indications of the annulus in this specimen. 



ScapJdtes ceqiialis, J. Sowerby. — The muscular attachment of the animal has also been 

 observed in an example of Scaphites (eqiialis, J. Sowerby, in the British Museum 

 Collection (larger of the two specimens, No. S9113). The specimen is an exceedingly 

 well-preserved and almost perfect natural internal cast from the Lower Chalk of Doi'set. 

 The greatest length of the specimen is 21) mm. ; the greatest diameter of the sejjtate 

 part (which is at the base of the body-chamber) is 15-5 mm., the whorl here being 9 mm. 

 high and 11 mm. wide (excluding the tubercles). The mouth-border is well preserved. 

 The anterior border of the muscular attachment is preserved on the lateral area as a very 

 faint line arising (on the leit side) almost close to the last septum and at about 1'5 mm. 

 from the edge of the whorl, and passing forward and towards the edge of the whorl 

 crosses this edge somewhat obliquely at about G'5 mm. in advance of the last septum. 

 Fortunately a portion of the body-chamber can be removed so that the course of this 

 line can be satisfactorily traced. Continuing still forward it passes into a fairly wide 

 shallow groove 4 mm. in front of the most anterior portion of the septate part of the shell, 

 the groove being disposed across the floor or concave portion of the body-chamber in a 

 flat forwardly-convex curve, with a very slight backward depression at the centre of the 

 area. A similar fine line can be somewhat less distinctly traced on the right side of the 

 specimen, passing into the same groove on the floor of the body-chamber. About 

 3 75 mm. posterior to the groove just mentioned there is another similar but narrower 

 groove. From my examination of other specimens it is not unlikely that this will prove 

 to be the posterior boundary of the shell-muscles, which seem to have been united on 

 the concave portion of the body-chamber into a fairly wide band. The shell-muscles 

 then appear to have been almost confined to the concave area of the body-chamber, only 

 a narrow portion extending on to the lateral area. 



In the British Museum Collection (No. C. GSOO) there is also a fragmentary example of 

 the same species (PI. 17. fig. 22), from the concave portion of the body-chamber of which 

 the matrix has been removed as carefully as possible. There is a similar line on the lateral 



