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The nudibranch family Dironidae, 
By 
F. M. MacFarland. 
Leland Stanford Junior University, California. 
With Plates 30-32. 
Among the various Opisthobranchs collected and studied by the 
writer on the Californian Coast the two which form the subject of 
the present paper are among the most interesting. Their characte- 
ristics set them apart so definitely from the other families of the 
group that it seems necessary to propose a new family for their 
reception. A brief description of some features of one of them has 
been given by Sir Cmartes Erıor (1905), based upon the study of 
a single specimen, collected by Prof. T. D. A. CockERELL at San 
Pedro, California, and aided by memoranda by the present writer. 
In his masterly Supplementary Part VIII to Auper and Haxcock’s 
British Nudibranchiate Mollusca ELior (1910) has again recognized 
the separate position of the Dironidae, the justice of which will, I 
think be evident to those who read the following pages. The 
limitations of space, however, prevent a complete treatment of the 
morphology of this group and many points of interest must be reserved 
for a future publication. 
The material has been collected at various times in the neigh- 
borhood of Pacific Grove, California, while enjoying the facilities of 
the Marine Biological Laboratory of Stanford University there. My 
thanks are due to the Directors, Professors GILBERT and JENKINS, 
for these eontinued privileges. To my wife Iam especially indebted 
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