MR. G. A. BOULENGER ON THE BOLTI. 345 



10. On Specimens o£ the Perciform Fish Tilapia nilotica 

 with increased number of anal spines. By Gr. A. 

 BOULENGBR, F.R.S., F.Z.S.* 



[Received Februarj' 1, 1916 : Eead April 4, 1916.] 



Index. 

 Vaeiation ; Page 



Variation in the number of anal spines in Tilapia 



Mi7o^Jc« and other Cichlidje 345 



Taxonomy : 



On the value of the number of anal spines for the 



division of the Cichlida; into genera 345 



Systematic : 



Tilapia nilotica atJiien.iis, yav. n.,T£. Africa. 346 



In the Cichlidfe, as in most Perciform Acanthopterygians, 

 three is the most frequent number of spines in the anal fin, and 

 this number may be looked upon as a primitive character. It 

 has generally been the custom for systematists to attach generic 

 importance to an increase in the number of these spines, even 

 when vmaccompanied by any other character. In this I have 

 differed, and refused to accept genera based on the number of 

 anal spines when everything else pointed to close relationship 

 with species showing the usual number, thus uniting Giinther's 

 Oreochromis (4 anal spines) with Tilapia and Pellegrin's Asta- 

 toreochromis (4 to 6 anal spines) with Haplochroiniis. I felt all 

 the more justified in doing so from the fact that occasionally, as 

 individual exceptions, the three spines may be increased to four, 

 as in Tilapia onossambica, variabilis, percivali, Haplochromis 

 desfontainesii. There is also the perplexing case of Cyrtocara 

 tnoorii, of which only two examples are known, one with three 

 anal spines, the other with four. My reform in classification 

 has not met with the approval of Dr. Pellegrin, who has 

 protested against the suppression of his genus Astatoreochroonis, 

 on the ground that the same character has been used for distin- 

 guishing American genera — with what regard to natural 

 affinities appears to me questionable. I think the following fact 

 disposes once for all of his objection. • 



It is with the greatest surprise that, on recently receiving 

 from Mr. S. L. Hinde a series of over 30 specimens of a fish 

 which I identified as the common Tilapia nilotica, a species with 

 which I am farailiar from a study of hundreds of specimens, the 

 first I took up showed five anal spines, and the others either 

 four or five. A table showing the variation in 30 of these 

 specimens is here appended. This series was obtained in the 

 Makindu and Isavo Rivers, affluents of the Athi River in 

 British East Africa. 



* Published by permission of the Trustees of the British Museum. , 



