SPONDYLUS. 



or other subject to which they adhere, but this does not 

 prevent them from constantly having' two small ears, one 

 on each side of the umbo, and a straight hinge line as in 

 Pecten. The Spondyli are always rough on the outside, 

 generally covered with spines and foliations of very varied 

 shapes ; sometimes the spines are subulate, sometimes ligu- 

 liform, some are sharp pointed, some are curved in various 

 directions and spatulate or foliated at their points, g'ene- 

 rally more regular and more like spines, and always ar- 

 ranged in rows upon radiating* striae or ribs on the upper 

 valve and such parts of the lower valve as are most free, 

 but in those parts of the lower valve, by which they become 

 attached, uniting- by their sides and spreading across many 

 ribs; sometimes all round the shell and producing a sort 

 of foliations or furbelows of very varied extent and shape: 

 very seldom does it happen that a Spondylus adheres only 

 by so small a space at the umbo as to leave the whole of 

 the lower valve free, but in such a case both valves are 

 covered with rows of spines. It is also remarkable, that 

 the upper valve and the spines particularly, are generally 

 more highly coloured than the lower valve or its spines 

 and foliations, in this respect there is sometimes a great 

 contrast between the two valves, the upper one being very 

 darkly and beautifully coloured, and the lower one scarcely 

 coloured at all. The umbones are unequal and distant, 

 being* separated from each other by a triangular flat area 

 between the umbo and the hinge of the lower valve, which 

 has the appearance of having been sliced off by a sharp in- 

 strument, and is divided by a longitudinal groove, in which 

 lie the decaying remains of that portion of the ligament 

 which is no longer useful: this groove is, however, fre- 

 quently covered over with shelly matter so as to be no 

 longer visible ; the area itself increases in length by age. 

 Hinge of the lower valve with two very strong teeth bent 

 backwards; a central hollow which is a continuation of 

 the groove in the area and to which the ligament is fixed, 

 and two lateral cavities for receiving the teeth of the upper 

 valve. Hinge of the upper valve with i\yo strong, also re- 

 flected, lateral teeth ; two intermediate cavities for receiv- 

 ing the teeth of the lower valve and a central hollow for 

 the ligament. The teeth of the two valves are so formed, 

 that without breaking away some portions of them or of 

 the circumjacent parts of the hinge, the two valves cannot 

 be separated; we have mentioned this fact before, in our 



