84 jNlE. G. C, CETCK ON THE MUSCULAE ATTACHMENT OP THE 



consists of the natural cast of only two wliorls. The aperture is not preserved, but a 

 portion of the last whorl without doubt formed part of the body-chamber. The larger 

 whorl is 30 mm. high (/. e. from the lowest row of tubercles to the suture of the shell), 

 and measures 65 mm. from side to side. The anterior border of the muscular impression 

 occurs as an impressed line very near the anterior end of the specimen. Viewing the 

 specimen with the large whorl downward, this line commences a little below the middle 

 of the whorl, and, crossing the uppermost of the three rows of small tubercles, turns 

 somewhat aln'uptly to the right, becomes more deeply impressed, and Avith a bold 

 anteriorly-convex curve crosses the other two rows of small tubercles and passes on to 

 the sloping surface below the tubercles, being intercepted at about 11 mm. below the 

 lowest row of tubercles by the broken anterior end of the specimen. 



Although the impression in this specimen is very incomplete, it serves to confirm the 

 structure which has just been described in Turriliies tuberculatus. 



Subg. Heteroceras, d'Orbigny. 

 Turrilites (Heteroceras) polyplocus, Roemer. — It is exceedingly interesting to have 

 been able to recognize any indications of the muscular attachment in this subgenus of 

 Ttirrilites, since here the shell is coiled in the opposite direction to that of the genus 

 Turrilites, and hence a corresponding inversion of the muscular attachment was to be 

 expected. The examj)le of Turrilites {Heteroceras) ^joIijjUocks, Eoemer, in which the 

 attachment has been seen forms part of the British Museum Collection (No. 461-51) and 

 is from the Upper Cretaceous rocks of Haldem, Westphalia (PI. 18. fig. 4). The specimen 

 consists of about one and a half whorls. The aperture is exceedingly well preserved, but 

 the suture-line is not shown, so that the base of the body-chamber cannot be thereby 

 recognized. The form of the right side of the attachment is seen in fig. 4. Viewing 

 the specimen as represented in the figure, the line indicating the anterior boundary of the 

 muscular attachment is seen as an impressed line to commence on the lateral area of the 

 whorl just to the riglit of the tubercle, which is above and somewhat to the left of the 

 aperture ; passing downward it turns to the left immediately under the tubercle, and 

 continues to pass downward for rather more than 20 mm. ; having turned upward 

 very slightly, it continues as a line of colour in a broad sweep, nearly parallel to the 

 outer curve of the whorl, to within about 60 mm. of the border of the aperture, when it 

 again becomes a finely-incised line ; then, turning upward and still passing forward for 

 about another 20 mm., it curves somewhat abruptly backward, continuing for about 

 20 mm. ; this last portion of the line enclosing an oval area, open posteriorly, the 

 diameters of which are 20 and 12 mm. respectively. This area I regard as one of 

 the muscular scars, and the line leading up to it as being partly the boundary of tlie 

 shell-muscle, and partly the boundary of the annulus. It is much to be regretted that 

 in developing the specimen its surface was somewhat scratched and rubbed, so that it 

 is not possible satisfactorily to foUow the course of the impression on the other side of 

 the whorl. 



