[3] THE OSTEOLOGY OF AMIA CALVA. 749 



able to discuss several questions of a more general nature, which aie of 

 prime importance when taken in connection with my work upon the 

 crania of the Teleostei, soon to be undertaken. It only remains for me 

 to justify myself for having- confined myself in this work, as I will in 

 those of the future, strictly to the cranium, and for having but touched 

 lightly upon those parts of the visceral skeleton connected with it; and 

 that, too, onlj'^ so much of it as was necessary to complete the form of 

 the skull. Such jjartiality would hardly be justifiable were one consid- 

 ering the forms the cranium assumes in the higher vertebrates. 



This is entirely different in the class Pisces. The visceral skeleton 

 here has, in so far as the cranium is concerned, preserved a certain 

 independence, and in consequence its form has been much less in- 

 fluenced, less so than other organic systems, as for example the nervous 

 System, the muscular system, and particularly the organs of sense. 



There is y-et another objection that might be brought forward, and 

 that is, that'I liave paid but little attention to the literature of the sub- 

 ject, particularly tbe older literature. In my allusion to facts long 

 known — ^"aud, as I assume, of facts well known — it seemed to me entirely 

 superfluous to continually cite authorities. Such a course would have 

 rendered my subject-matter diffuse and unwieldy, without adding any- 

 thing useful. The literature relating to it, contained in the more recent 

 and less known works, and "which refers to the discussion of purely 

 special points, I have in every instance conscientiously cited. 



Through the unbounded liberality of Privy Counselor Mr. Gegenbaur, 

 to whom 1 here exjjress my profound thanks, I have been enabled to 

 examine five specimens of Amia, the smallest of which was 36'=™, the 

 largest 57«'" long. 



In viewing an unprepared head of Amia calva one can already dis- 

 tinguish the superficial plates of bone that overlie the cranium, they 

 being merely covered by an extremely thin cutis.^ 



The sculpturing of the superficies of these bony plates is quite char- 

 acteristic, consisting of sharply-defined and numerous ridges, which 

 start from the center of each bone, to radiate outwards to the peri- 

 pheries. After the thin skin covering them has been carefully removed 

 one recognizes the limits of the several bones with requisite distinct- 

 ness. Three pairs of bony tables, situated one behind the other, first 

 meet the eye, of which the foremost possesses the greatest and the 

 hindmost the least longitudinal extension. 



The foremost of these pairs of plates consists of two bones, each of a 

 quadrilateral outline, being joined together mesially by a strong dentated 

 suture. (Plate I, Fig. 1.) The lateral borders of these bones arch over 



*If Bridge {loo. cit., page 606) describes the surface of these bones as "highly pol- 

 ished," and further says "they arc destitute of any covering of soft skin," he is in 

 error. One can easily convince himself, from a microscopical examination, that all of 

 these overlying iilates of the skull in Amia are not only covered by an epidermis — 

 Avhich is also present is Lepidostem and Pohjpterus — but undoubtedly also possesses a 

 very thin covering of cutis. 



