200 INTESTINAL STRUCTURE OF FOSSIL FISHES, 
of fishes, or the contents of their intestines, still 
retaining the form of the tortuous tube in 
which they were lodged. To these remarkable 
fossils he has given the name of Cololites. (PI. 
15' is copied from one of a series that are en- 
graved in Goldfuss. Petrefacten, PL 66.) He 
has also found similar tortuous petrifactions 
within the abdominal cavity of fossil fishes, be- 
longing to several species of the genus Thrissops 
and Leptolepis, occupying the ordinary position 
oi the intestines between the ribs.* (See Agas- 
siz Poissons Fossiles, liv. 2, Appendix, p. 15.) 
* As these Cololites are most frequently found insulated in 
the lithographic limestone, M. Agassiz has ingeniously explained 
this fact by observing the process of decomposition of dead 
fishes in the lakes of Switzerland. The dead fish floats on 
the surface, with its belly upwards, until the abdomen is so 
distended with putrid gas, that it bursts : through the aperture 
thus formed the bowels come forth into the water, still adhering 
together in their natural state of convolution. This intestinal 
mass is soon torn from the body by the movement of the 
waves ; the fish then sinks, and the bowels continue a long 
time floating on the water ; if cast on shore, they remain 
many days upon the sand before they are completely decom- 
posed. The small bowels only are thus detached from the body, 
the stomach and other viscera remain within it. 
We owe this illustration of the nature of these fossil bodies, 
whose origin has hitherto been inexplicable, to the author of a 
most important work on fossil fishes, now under publication 
at Neuchatel. His qualifications for so great and difficult a 
task are abundantly guaranteed by the fact, that Cuvier, on 
seeing the progress he had made, at once placed at the disposal 
of Professor Agassiz the materials he had himself collected 
towards a similar w’ork. 
