Note 84 — 1. Genus—BALANUS, Auct.[83]

In some specimens of Balanus perforatus I made the following enumeration of the number of segments in the cirri:—

Basal diameter of shell 1/20th of an inch. Basal diameter of shell 1/5th of an inch. Medium sized specimen about 3/4ths of an inch in basal diameter.

First cirrus shorter ramus ?1117

Second cirrus 4 or 5913

Sixth cirrus 9 or 101931, in another 36

In the specimen 1/5th of an inch in basal diameter, each segment of the posterior cirri carried five pairs of spines; whereas, in full-grown specimens, there are six or seven pairs. In the 1/20th of an inch specimen, on the inner maxillæ, there were no spines between the upper large and the lower large pair of spines; whereas, in the 1/5th of an inch specimen, there were five intermediate spines, and in larger specimens nine or ten spines.