608 



SHELLS OF THE UPPER LUDLOW ROCK. 



" From these and other circumstances to be presently mentioned, and from their mechanical 

 structure, there can, I think, be little doubt that the masses in question are really coprolites. I 

 confess, however, that I should hardly have arrived at this conclusion, had I not before repeatedly 

 examined coprolites, and witnessed the variety to which they are liable. 



"I have alluded above to certain other circumstances corroborative of the opinion advanced. 

 These relate to the origin of the principal materials of which our e supposed coprolites ' are com- 

 posed, and may in conclusion be briefly stated. 



c< The mass of the bed, containing these concretions, consists almost entirely of a congeries of 

 various organic remains. Of these organic remains, two kinds strikingly predominate. One kind, 

 and by much the most abundant, consists of fragments of bones (scales or spines), for the most part 

 of a dark or black colour. The other kind of organic remains differs altogether in texture and ap- 

 pearance from the black fragments, and is of a reddish brown colour. The black organic fragments 

 I find to consist of phosphate of lime and of carbonate of lime; and there is left, undissolved in the 

 acid employed, some carbonaceous and other matters. The reddish brown fragments consist also 

 of carbonate of lime and phosphate of lime, but the phosphate of lime appears to be in much less 

 proportion than in the black fragments. The composition, therefore, of these organic remains seems 

 to account very satisfactorily for the origin of the phosphate and carbonate of lime in the Supposed 

 coprolites.' " — Letter from Dr. Prout. 



The small shells {Orbicula rugata, f. 47 and 48 ; Lingula minima, f. 49 ; Bellerophon globatus? 

 f. 50; Turritella, f. 51 ; and Ortlioceras semipartitnm, f. 52 and 53.), as well as the cast of a cri- 

 noidal column, f. 54, were found both in the coprolites and diffused through the layers. 



FOSSIL SHELLS OF THE UPPER LUDLOW ROCK. 



Described by Me. James de C. Sowerby. 



PLATE V. 



Serpulites longissimus, f. I. 1 Very long, hardly diminishing in diameter, compressed, smooth, 

 slightly tortuous, composed of numerous thin layers of shell containing much animal matter. 



No part of this extraordinary fossil has been observed attached to other bodies ; it forms large 

 curves, sometimes almost circles, occasionally even a foot in diameter. The tube is so much 

 compressed that its sides nearly touch, and that this is the effect of pressure is shown by the 

 form it has assumed. Those parts which were nearly perpendicular to the direction of the 

 compressing force have resisted pressure most powerfully, and fractures have taken place in 

 longitudinal lines near such parts. The quantity of animal matter in the laminae gives them 

 an opalescent appearance. In structure, this fossil resembles the Serpula compressa of Min. 

 Con., tab. 598. f. 3 ; but it does not diminish so rapidly. Width \ an inch. 



1 In the description of the Upper Ludlow Rock this fossil has been inadvertently named Serpuloides lon- 

 gissima. 



No naturalist who has examined this form has been able to throw any light upon its true place in the animal 

 kingdom, and I have therefore named it provisionally Serpulites longissimus . — R. I. M. 



