282 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY 



Species. 



Pre- 



atrioporal. 



Pre- 

 anal. 



Post- 

 anal. 



Total. 



Authority. 



B. caribbceum 



35 



14 



9 



58 



Andrews. 



j > 



36 



14 



9 



59 



Andrews. 



)5 



37 



14 



9 



60 



Andrews. 



>,J 



37 



15 



9 



61 



Kirkaldy. 



) > 



35 



15 



10 



60 



Andrews. 



B. lanceolatum 



35 



15 



10 



60 



Andrews. 



>i 



36 



15 



10 



61 



Lankester. 



3> 



35 



14 



11 



60 



Kirkaldy. 



»J 



35 



14 



12 



61 



Andrews. 





36 



14 



12 



62 



Andrews. 



5> 



36 



14 



13 



63 



Andrews. 



>> 



37 



14 



12 



63 



Andrew's. 



5. belcher i 



37 



14 



13 



64 



Giinther. 



»> 



37 



16 



10 



63 



Kirkaldy. 



»j 



37 



16 



11 



64 



Tattersall. 



>> 



37 



17 



10 



64 



Tatter sail. 



>.j 



37 



17 



9 



63 



Tattersall. 



>' 



38 



17 



9 



64 



Tattersall. 



The last four formulae are taken from Professor 

 Herdman's Ceylon material. 



The transition from one species to the other is most 

 gradual, and no reason can be given for separating the 

 forms at an y particular point. In fact, we find that 

 two specimens with the same formulae are put down as 

 different species. It may be mentioned that li. caribbcEum 

 often has as many as 38 pre-atrioporal myotomes, and so 

 approaches B. belcheri. 



B. belcheri seems to be rather more distinct than the 

 other two, but still the transition is seen to be quite 

 gradual. 



To make the inconsistency noted above all the more 

 evident let us now consider ^4. bassanum. The total 

 range is from 70-78, yet, as noted above, three species 

 have been distinguished within a similar range. The 



