December 8, 1911] 



SCIENCE 



801 



NOTE ON THE OHIO PLACODERM 

 DINICHTHYS TEERELLI 



In a recent paper' Professor Branson de- 

 scribes and figures a specimen of the Devonian 

 " fish " Dinichthys terrelli, in the Oberlin col- 

 lection — a specimen evidently of great value, 

 for it- presents for examination many parts, 

 largely in their natural relations, of one and 

 the same individual. Similar specimens, as 

 one recalls (not without chagrin) have earlier 

 been found, and possibly even better ones, but 

 their parts have never been kept together : for 

 the zeal of pioneer collectors led them to sepa- 

 rate all possible plates from the matrix, and 

 caused the destruction of smaller undetaehable 

 elements, leading, naturally, to a less complete 

 understanding of the anatomy of the " fish." 

 In the present case Dr. Branson has been able 

 to add interesting notes to our knowledge of 

 this classic fossil; he has shown especially that 

 the " clavicular " element of this species is 

 smaller in its proportions than has hitherto 

 been described, and he notes, very justly in this 

 regard, that the restoration of the huge head 

 of D. terrelli exhibited in the American Mu- 

 seum of Natural History, " makes the animal 

 much thicker dorsal-ventrally than it should 

 be." His comments, however, are less con- 

 vincing which concern the actual relations of 

 this plate. "We have known that its upper 

 part fitted betweenythe antero-dorso-lateral and 

 the side of the cranium, we have not known, 

 though, just how the plate was placed at the 

 side of and below the suborbital, and the 

 present specimen, in spite of its many vir- 

 tues, does not appear to clear up this point. 

 Dr. Branson's conclusion that " the inner arm 

 of the clavicular must have come inside the 

 clavicular and prevented the mandible from 

 resting against it " is not quite evident, since 

 it is based upon a " left clavicular (which) lies 

 on the right side, on top of the right clavicular 

 which has lost its lower end." For, unhap- 

 pily, it is the lower end of this plate which 

 concerns us, and we can not, therefore, feel 

 sure that .a plate which has become detached 



^University of Missouri, Bulletin, Vol. 2, No. 2, 

 October, 1911. 



and shifted, will make clear its real relations 

 to the plates near which it happens to lie. 

 We may note in passing that several elements 

 are present in the Oberlin specimen which, as 

 far as we can judge from the picture, appear 

 to have been earlier described, but never rela- 

 tively in their natural positions; one of these 

 is here shown close to the outer end of the 

 interlateral plate, near a point where another 

 plate should occur, by analogy with Coccos- 

 teus, but where no element is definitely known. 

 Bashford Dean 



the number of students to a teacher in 

 state colleges and universities 



To THE Editor of Science: In the table 

 published in your issue of October 27 the 

 University of Minnesota was listed as having 

 one teacher to every twenty-six students. The 

 situation in this institution is by no means 

 what it should be in this regard, but the ratio 

 indicated above is so wide of the mark that I 

 immediately looked up the figures upon which 

 the estimate was based. A copy of the report 

 to the Commissioner of Education is on file 

 here. An examination of the report shows 

 that in the total number of students all the 

 students in the schools of agriculture, which 

 are schools of secondary grade, were included. 

 On the other hand the instructors in these 

 schools were not included in the total of teach- 

 ers. When this correction is made the ratio 

 is changed from 1 to 26 to 1 to 16. As an 

 average for all departments of the university 

 this is probably approximately correct. 



It seems desirable that some system of uni- 

 form and comparable statistics should be 

 worked out. For example, there seems to be 

 no definite understanding as to what consti- 

 tutes a " teacher." Is a man giving himself 

 wholly to research in a laboratory or in an 

 observatory to be reckoned as a teacher ? Is a 

 clinical professor who gives part of his time to 

 instruction in a school of medicine to be 

 counted as a whole teacher, or such fraction 

 of a teacher as is determined by the propor- 

 tion of normal instruction which he offers ? 



The " students " need to be more carefully 

 defined. Is the unit the individual without 



