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aquatic JUfe 



but two species, namely Umbra limi and 

 U . pygmaea; the Lucidae, with the sin- 

 gle genus Lucius, or the pikes contained 

 in some seven species ; the Poecilidae or 

 Killifishes includes some twenty genera, 

 with an enormous number of species. 

 Finally we have the Amblyopsidae, or 

 blind fishes of the caves, with three gen- 

 era and some five different species. 



Of all these I have paid more atten- 

 tion to the pikes ; that is, in so far as 

 their structure is concerned, and, to tell 

 the truth, while we know something of 

 the anatomy and the relationships of this 

 host of forms, we are, for the most part, 

 woefully ignorant of nearly everything 

 concerning it. Dr. David Starr Jordan, 

 in touching upon this matter, has said : 

 "While our knowledge of the osteology 

 and embryology of most of the families 

 of fishes is very incomplete, it is evident 

 that the relationships of the groups can- 

 not be shown in any linear series, or by 

 any conceivable arrangement of orders 

 and sub-orders. The living teleost fishes 

 have sprung from many lines of descent ; 

 their relationships are extremely diverse, 

 and their differences are of every pos- 

 sible degree of value." 



This difficulty will ever confront us, 

 and we will remain in the dark as to the 

 vast majority of the relationships of ex- 

 tinct and living forms of teleostean fish, 

 — indeed of all fishes, until we are more 

 familiar with their structure or morphol- 

 ogy. It has been and is now shamefully 

 neglected. For many years past I have 

 collected osteological materials of many 

 of our best-known bony fishes, and pho- 

 tographed their skeletons. In some in- 

 stances descriptions have been written 

 out ; but all my efforts, in many direc- 

 tions, failed of publication in the United 

 States. At this writing there seems to 

 be very considerable hope that a good 

 part of it will be published in Australia, 

 where the value of such information is 



keenly appreciated and sought after. 



The mud fishes of the genus Umbra 

 are found in Austria and in this country. 

 As a genus, according to Doctor Jordan, 

 they are characterized by having no 

 lateral line; the scales are of medium size 

 and unstriated (cycloid type), with ex- 

 ternal characters easily studied in my 

 photographs of Umbra pygmaea, speci- 

 mens of which I have kept in aquaria for 

 months together, in that I might study 

 the habits of the species and make photo- 

 graphs of them. Two of the latter, made 

 by me from life in February, 1917, are 

 here reproduced to illustrate the present 

 article. I know of but two species of 

 Umbra that have thus far been described 

 as belonging in our fish fauna, that is, 

 U. limi, of the central section of the 

 United States and lower Canada, with 

 the form very closely related to it, the 

 above mentioned U. pygmaea, which has 

 been called the Eastern Mud Minnow. 

 It is said to range from Long Island to 

 the Neuse River, being often abundant 

 locally. My specimens of Umbra are 

 from swampy holes along the Potomac 

 River, near Washington, where I cap- 

 tured them myself. 



Recently I have made some studies of 

 Umbra limi and Umbra pygmaea, and 

 carefully compared them. Most of the 

 material studied by me belongs to the 

 collection of fishes in the Division of 

 Fishes of the United States National 

 Museum, and I am greatly indebted to 

 Dr. Barton A. Bean, curator of that 

 division, for his kindness in placing all 

 that material before me, as well as for 

 inviting my attention to various pub- 

 lished accounts of these different species 

 of mud minnows of the genus here to be 

 considered. I have also studied living 

 specimens of the form of Umbra found 

 in the District of Columbia, in one of the 

 aquaria belonging to Mr. James E. Bene- 

 dict, Jr., of Washington, D. C, to which 



