P0LLIC1PRS MITELLA. 321 



tulum. The attached portion, which is moderately pointed 

 in young specimens, becomes extremely broad in old spe- 

 cimens. The calcified scales sometimes differ a little in 

 size, in specimens of the same age : they are always com- 

 pactly and symmetrically arranged : in old specimens they 

 are much larger than in young ones : each scale has, 

 at first, a transversely elliptic growing base, which ulti- 

 mately becomes nearly circular. Exteriorly the tips of 

 the scales are always disintegrated ; they are sometimes 

 club-shaped, owing to the scales having been re-added to 

 after a period of reduced growth. The scales are fringed 

 with brown disintegrating membrane. 



Attachment, — At the base of the peduncle, the two 

 cement-ducts running together, twist about in a singular 

 manner, and at their bends pour forth cement. According 

 to the age of the specimen, the ducts vary in diameter from 

 5~th to Keiths of an inch. The two cement glands are 

 small and difficult to find ; they are retort-shaped, with two 

 ovarian tubes entering each. They lie close together, in 

 nearly the centre of the peduncle, and less than half-way 

 down it. This proximity of the two cement-glands, and 

 their position low down the peduncle, are of interest in 

 relation to the position of these same glands in the sessile 

 Cirripedes. 



Size and Colours. — This is the largest and most massive 

 species in the family. I have seen one specimen in the 

 British Museum, from the Coast of China, 2*3 inches 

 across the capitulum, and 1*5 in length, with the valves 

 surprisingly thick. The relative width and length of the 

 capitulum varies. The sack (in specimens long kept in 

 spirits) is dirty purple, and exteriorly between the scuta, 

 dark purple. The cirri, tropin, penis, caudal appendages, 

 three posterior segments of the thorax, and the abdominal 

 surface are dark-brownish purple. 



Body. — Thorax remarkably compressed and carinated ; 

 prosoma pretty well developed. Extending from the base 

 of the second cirrus, to nearly a central line on the thorax, 

 there is on each side a rounded ridge : there is a second 



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