200 Mr. R. Walker on Clays, containing Fossils, 



The Antipathes Larix which I had in my possession had its 

 convolutions crammed with corpuscles resembling in transpa- 

 rency and tint the testicular capsules of Gerardia. If it were 

 not rash to come to any conclusion from observations made on 

 objects not in the best possible state, 1 should say that the sexes 

 are separate, and borne not only by distinct polypes, but even 

 upon distinct polyparies. But I cannot generalize and assert 

 that this is always the case. 



The polypary of the true Antipathes bristles all over with 

 spinules. These have not escaped other writers, but some of 

 them have erroneously regarded them as abortive branches. The 

 arrangement of these spines may furnish useful characters for 

 the discrimination of the species. 



The sarcosoma everywhere covers the polypary, which appears 

 as if enclosed in a sort of distinct sheath. When it contracts, its 

 tissue is traversed by the spicules, as is the case in the Gorgonia. 



The growth of the polypary takes place by the deposition of 

 layers which are superimposed upon the stems, and which at 

 the extremities resemble the fingers of gloves enclosed one within 

 the other. The centre of the axis appears to be perforated by a 

 canal ; but this is only an appearance due, in fresh individuals, 

 to the inferior density of the substance which has been added at 

 the extremities and become internal, and, in dried specimens, to 

 the contraction of this substance. 



Between Gerardia and Antipathes there are great differences. 

 In the former the polypary is smooth and covered with very 

 small and scarcely sensible umbilicated elevations; in Anti- 

 pathes it is covered with spinules. The twenty-four tentacles of 

 Gerardia correspond with as many chambers separated by the 

 same number of septa with convoluted filaments ; in Antipathes 

 only two of these convoluted cords are developed, and the tenta- 

 cles are never more than six in number. In Gerardia the Acti- 

 nian type is as highly developed and characterized as possible ; 

 in Antipathes it remains incomplete, in consequence of a sort of 

 arrest of development. 



XXIV. — On Clays, containing Fossils, near St. Andrews ; with 

 Remarks on some of the latter. By Robert Walker. 



The Clay- bed whose geological position and fossil contents are 

 about to be noticed is situated near the mouth of the Kinness 

 Burn, or rivulet, a small stream that runs past St. Andrews on 

 the south side. Towards the sea this stream has eroded its 

 channel about three feet through the bed. At one time the 

 clay could be seen forming part of the bank on each side of the 



