55 
founded the last fin ray was characterized by its sigmoid 
curve and horizontal position. ‘These features were doubt- 
less anomalies. 
10.—Anat Fin (Figs. 18 and 19). 
The mechanism of the fin rays and their skeletal 
supports is the same as in the dorsal fin. The axonosts 
are, however, perceptibly longer than those of the latter 
fin, and they are sometimes called interhaemal bones to 
distinguish them from the interspinous elements. The 
structure of the anal axonosts is the same as that of the 
dorsal ones. 
The anterior extremity of the anal fin is interesting 
in many ways. ‘The posterior boundary of the body cavity 
is supported by a very stout bone which curves downwards 
and forwards from its roof, and terminates in a point 
behind the anus. Above it fits into a deep recess borne 
on the anterior face of the haemal spine of the first caudal 
vertebra (fig. 13, Lec.Aa.'). The ventral point, to an 
extent indicated in fig. 18 by a ring, is in dead specimens 
almost invariably found perforating and projecting freely 
through the skin behind the anus. It seems highly im- 
probable that such a pathological condition can obtain 
during life, but the skin covering the point must be very 
thin.* This bone, in the lack of any evidence as to its 
development, is here called the first axonost, but it is 
certain that it is more than this. In no other part of the 
body is a baseost situated anywhere but between two 
* We are now certain that the point does not perforate the skin during 
life, but that the latter is somewhat easily ruptured when a plaice is 
handled and allows the point to protrude. Also that the protrusion in dead 
specimens is due to contraction following on preservation. To make use, 
therefore, of this so-called external ‘‘ anal spine’’ in classification, as has 
hitherto been done, is absurd. Since this was written, we note that Kyle 
arrives at the same conclusion. 
