April 29, 1887.] 



8CIEJSrCE. 



415 



average of the measurements secured from fifty or 

 more skulls or other parts of the skeleton. So, 

 too, with our descriptions of such material, for we 

 must remember, that, as important as the detailed 

 account of the skeleton of any species of vertebrate 

 may be, it will in no case exactly apply to the skele- 

 ton of another specimen of the same species, every 

 thing else being equal. 



This being the case, we should endeavor to have 

 before us as large a series as possible of skeletons of 

 the particular form or species we may be describing 



of the skull of our violet-green swallow (Tachycineta 

 thalassina). This drawing isperfectin all its details, 

 and the subject was chosen from a series of a number 

 of others. Notwithstanding this, fault was found 

 wath it in certain quarters, and it was said that the 

 maxillo palatines of the specimen were broken off, 

 whereas in reality nothing of the kind had happened , 

 the specimen being an unusually perfect one, al- 

 though in it these parts were shorter than they com- 

 monly occur. (I have since learned with regret that 

 the person who had this fault to find, for it did not 



RIGHT LATERAL VIEW OF SKULLS OP X. XANTHOCEPHALUS (X 2). 



pp, pars plana ; na, nasal ; mxp, maxillo-palatine ; v, vomer ; mx, maxillary ; pi, palatine ; pt, pterygoid • 



ms, mandibular sesamoid ; q, quadrate. ' 



with the view of giving a published account of its 

 osteology to the world. When this is the case, it is 

 sure to reveal its advantage in our account by the 

 character of our description, and the weight we 

 attach to the length of a process here, the form that 

 a certain part may assume there, or the size, pres- 

 ence, or absence of vacuities and foramina, and 

 similar details. To better illustrate my meaning, I 

 would cite the following example : last winter I pub- 

 lished in the Proceedings of the Zoological societj'^ of 

 London a contribution to the comparative morphol- 

 ogy of the swifts, humming-birds, and goatsuckers ; 

 and among the figures in the text was a drawing of 

 mine, twice the size of life, giving the basal aspect 



constitute criticism, had not a single specimen of the 

 species before him, or available, at the time he pub- 

 lished his remarks ! ) Students of human craniology 

 who have studied long series of skulls from individ- 

 uals of the same race, will at once appreciate the 

 point I desire to convey here ; for how often do we 

 find, say, in one skull, a styloid process, for exam- 

 ple, perhaj)S an inch or more in length, whereas in 

 another specimen from the same series it will be 

 represented by the most insignificant apophysis im- 

 aginable ! 



For a number of years past I have been collecting 

 material to illustrate the very point about which I 

 am now writing ; and among this material I find 



