LEODICID.E OF THE WEST INDIAN REGION. 7 



5. The gills: These are usually attached to the dorsal cirrus, but in some cases 

 they arise on the body wall dorsal to this. Their form and mode of branching, as well 

 as their distribution over the body, are quite constant within the limits of a species. 



6. The setce: Three forms of setse occur, simple, compound, and pectinate, 

 the latter being characteristic of the family. The simple setse are always slender 

 and sharp-pointed, sometimes with a "wing" or "fin" along one or two edges. 

 In some cases this wing is really two flattened expansions diverging and making 

 an acute angle with each other from the side of the shaft. Whether this is always 

 the case I can not say, but it seems probable that it is. Sometimes, also, it is clear 

 that what appear as wings on opposite sides of the shaft are really these two 

 parts of the wing which, instead of appearing in profile and therefore looking like 

 one, are seen in half or full face. The compound seta is usually toothed at the 

 end and covered by a "hood," which in reality is a pair of thin plates lying one on 

 either side of the apex of the terminal joint. When seen in profile, which is their 

 usual position under the microscope, this looks like a covering of the entire end. 

 In Morphijsa, compound setae occur whose terminal joints are not toothed and do 

 not have a hood. The pectinate setse are much broadened and flattened toward the 

 end, this flattened part being more or less curved to form a scoop-shaped portion 

 whose margin is drawn out into a number of very delicate, sharp-pointed teeth. 



7. The anal cirri: Usually characteristic in form and size in any species. 



1. Diagram of Leodicid maxilla. 2. Diagram of mandible. 



8. The jaws: While regarded by some students of the family as too variable 

 in individuals and too similar in different species to be of value in classification, 

 I have found that while such details as the number of teeth in a plate may vary, 

 the general appearance and the arrangement of parts of these structures are 

 decidedly characteristic in any species. Especially in the jaw of Leodice there is 

 apt to be confusion in following the description without some definite plan of 

 nomenclature, and in the descriptions I have followed the scheme indicated in 



