SYSTEMATICAL ACCOUNT 



lam. EüPS VMMIDA1 . 



Th< i general rule in the relation between the septa in tliis family. Of the twelve 



priginal sepia Lacaze-Duthiers 1897) s ' x become the septa of the hrst order and ilrst cycle, 



six alternating ones becoming the sepia of the second order. The .septa of higher orders 



are formeel two at a time, always at one side only of the septa of the second order. They 



ihorter than the latter, with which they are united by their central ends. In this way we 



septa those of the second. third and fourth order forming a triangle whose 



is the section of the margin enclosed by the septa of the second and third orders, and 



whose apex points towards the columella, but does not reach it. rhe septum of the fourth order 



forms an axis of symmetry between the two others, being in line with the central portion of 



the septum of the second order, whose peripheral portion bends ontward to form one of the 



sides of the triangle. It may he clear from this that my septum of the fourth order is the 



same as the septum of the second order or cycle of authors. 



The formation oi septa ol higher orders goes on in the same way, always two septa 

 at the sanv time, which unite with the older septum to form triangles in which the septum 

 of the highest order is the a.\is of symmetry. Newly formed sepia unite always with the lateral 

 ita, never with the axis of symmetry of the triangle. 



The formation of new septa goes on taster at the side of the older of the two lateral 

 i. thus establishing it as a se], umi of lower order. So we get again an asymmetry. This 

 asymmetry maj be temporary or permanent. But it is difficult if not impossible to say which 

 it is in a given 



It may 1- ar trom this that there is no real difference between the genus Balano- 



phyllia and the genus Rhodopsammia: the difference being based on an assumed difference 



the septa. s., the genus Rhodopsamtnia must be absorbed in Balanophyllia. 



I found the same relation between the septa of different orders in all the genera of the 



immidae that I < ould e :amine, except two, viz. Stephanopliyllia and Leptopsammia. According 



e-Edwards and II umi, the genus Endopsammia wholly agrees with Leptopsammia in 



to thi 1; maj be il is better to unite these two genera in a single one. P01 ri \i 1 - 



• this genus Trochopsammia has noi cent septa; 1 could not examine that 



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