Ilie Stomodceum, Mesenterial Filaments, $c., of Xenia. 443 



on the snout forms a very distinct "shell-breaker," which seems to 

 be represented in the adult by the large median scale in front of 

 the premaxillse. 



(15) At about the time of hatching there are on each of the 

 premaxillsD three distinct, sharp, conical teeth, of which the outer- 

 most is the largest. These probably unite later on to form the 

 large upper cutting teeth of the adult. There are also three similar 

 teeth on each side in the front of the mandible, which probably 

 unite to form the lower cutting teeth of the adult. (I have not 

 found any vomerine teeth.) 



Of the above results those regarding the amnion and the parietal 

 eye seem to be the most interesting. I had discovered and drawn 

 the posterior amniotic f canal long before I was aware of Mitsukuri's 

 similar and previous discovery in Chelonians, and it appears to me 

 that the observation is of especial interest in view of the supposed 

 relationship between Sphenodon and the latter group, the probability 

 of which is greatly strengthened by the striking similarity in the 

 development of the fostal membranes. 



The development of the parietal eye in Sphenodon certainly sup- 

 ports Beraneck's important conclusion that this organ (in Lacerta and 

 Anguis) arises independently of the epiphysis, a conclusion which 

 was also unknown to me until after I had come to suspect the same 

 thing from observing the peculiar relation of the stalk of the parietal 

 eye to the posterior commissure. 



I may add that owing to the scarcity of biological literature in 

 Christchurch the works of Mitsukuri and Beraneck above referred 

 to are only known to me from the short abstracts in the ' Journal of 

 the Royal Microscopical Society.' 



" The Stomodseum, Mesenterial Filaments, and Endoderm of 

 Xenia" By J. H. ASHWORTH, B.Sc., Demonstrator in 

 Zoology, Owens College, Manchester. Communicated by 

 Professor HiCKSON, F.R.S. Received February 23, Read 

 June 16, 1898. 



The specimen referred to in this note is a colony of the Alcyona- 

 ceous coral Xenia sp. ? from Celebes. The Xeniidae are distinguished 

 from all other Alcyonaria by their soft fleshy consistency and 

 non-retractile polyps. The former character is due to the fact that 

 their spicules are very minute rounded or oval discs (average measure- 

 ments 0*015 mm. long, O'Ol mm. broad, 0'004 mm. thick), which have 

 a horny basis impregnated with only a small quantity of calcium 

 carbonate. The polyps have the usual Alcyonaceous structure, and 



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