ON THE CHITINOTIS OBGANS IN THE CHEILOSTOMATA. 357 



Supplementary Note respecting the Use to be made of the 

 Chitinous Organs in the Cheilostomata in the Diagnosis of 

 Species, and more particularly in the Genus Cellepora. 

 (Plates XXVI. & XXVII.) 

 I much regret that before drawing up the preceding account my 

 attention had not been called to a suggestion by Mr. Arthur W. 

 Waters* respecting the use of the characters afforded by the oral 

 valve or operculum in the diagnosis of species in the Cheilosto- 

 matous Polyzoa, as I should otherwise have been saved a great 

 amount of time and trouble in the endeavour to establish satis- 

 factory distinctive characters in the perplexing and difficult group 

 of the Cellepores. 



But having since devoted much attention to this point, and 

 examined the characters, not only of the operculum, as suggested 

 by Mr. "Waters, but also, in addition, those of the other chitinous 

 elements of the skeleton in between sixty and seventy species of 

 Celleporce, as well as in numerous species of Reteporce and Sali- 

 comariadce, both groups in which the determination of species is 

 often attended with considerable difficulty and uncertainty, I 

 have become convinced that the characters derived from the 

 chitinous organs will be found of the greatest possible utility, 

 and at the same time capable of being employed with the utmost 

 facility and precision. 



In fact, so far as my present experience teaches, it appears to 

 me that the characters derived from these parts of the skeleton 

 will prove, at any rate in the three generic groups above mentioned, 

 almost alone sufficient to determine specific distinction or affinity, 

 so that from a very minute fragment of a zoarium, if in the 

 proper state of preservation, the species may, in a few minutes, 

 be made out with the utmost ease. 



How far the characters of these appendages may be of use 

 with respect to generic or more general distinction, I am not at 

 present prepared to say, and much doubt whether they will be 

 found extensively useful in that regard. 



But at present I am convinced that in future it will be in- 

 dispensably requisite in the definition of a species, at any rate in 

 certain denned natural groups, to give the characters of the 

 chitinous organs, which are certainly of equal, if not greater, 

 value than those afforded by the calcareous skeleton alone. 



* " On Bryozoa," Proc. Literary & Philos. Soc. Manchester, 1878, vol. xvii. 

 p. 125. 



