SEA-FANS AND SEA-PENS 153 



what firm crust. This, in dried specimens, breaks off readily. 

 The colony branches profusely, or rather separates by fission, in 

 one plane, the large and small branches making a network of 

 fan-like shape and often of great fineness and intricacy. These 

 fans attain a length of several feet and a corresponding breadth, 

 and are abundant in semi-tropical as well as in more southern 

 waters. In color they are red, yellow, brown, or purple. 



ORDER PENNATULACEA 



SEA-PENS 



These singular colonies resemble quill-feathers, such as are 

 used for pens, and are named for this reason. The long, horny 

 central axis is naked below, ,and is partly buried in the sand, but 

 is not permanently attached. The upper portion of the axis has 

 two rows of short, opposite, lateral branches ; on the upper side 

 of the branches the polyps live in separate inclosures. Spicules 

 of lime are present in the substance of the branches, which gives 

 them stability. Sea-pens are found at moderate depths and are 

 widely distributed. They are highly colored and phosphorescent. 



