284 Papers from the Marine Biological Laboratory at Tortugas. 



years ago on the wild coasts of a new and savage world, one must marvel 

 at the care and minute accuracy with which he did his work. He says: 



The mouth is 23^ inches wide, toothless, but having in the place of teeth a lower jaw 

 in the shape of a tongue. This is 4 inches long, 1 3^ inches wide, and reaches to the external 

 opening of the mouth. Likewise there is an upper jaw placed crosswise, 2 inches long 

 and as many wide. The lower jaw consists of 17 hard white bones having the shape of 

 the letter U and joined firmly to the membranes. Underneath there lie 17 other bones, 

 one under each, of spongy appearance, but not so hard. The upper jaw consists of 14 

 bones, shaped like the letter J and also joined together by membranes. Likewise there lie 

 above these 14 other bones. Moreover the two jaws are joined to the other bones of the 

 head by membranes [cartilages?]. 



If the reader will now turn to figures 22 and 23, plate ix, he will see 

 photographs of the remarkable dental armature of this fish. The coinci- 

 dence may be noted here that the jaws of my 1909 specimen had exactly 

 the number of teeth given by Marcgrave. He speaks of the lower jaw being 

 toothless, but consisting of a tongue-shaped bone 4 inches long, i3^ inches 

 wide, and reaching to the lips. My original notes, made before reading 

 Marcgrave, describe the jaws as being like the slipper-shaped stirrup of 

 a woman's side saddle, the lower jaw being the slipper or bottom part of 

 the stirrup. In illustration see figures 22 and 23, plate ix, of the jaws, and 

 figure 2, plate i, and figure 19, plate viii, in which the lower jaw is seen pro- 

 jecting from the mouth. Six complete sets of measurements of as many jaws 

 of Beaufort specimens will be given later and four sets for Key West rays. 



What Marcgrave meant by his statement that in the upper and under 

 jaws there are other bones, one under each tooth, I am at a loss to under- 

 stand, unless it be that he refers to the spongy foundation part of each tooth. 

 So Schneider (1801) conjectures when he says that Willughby (whom he 

 seems to have known as a mere copier of Marcgrave) probably refers to the 

 crenate base or some other part subjacent to the teeth for the "under " spoken 

 of in the description. The teeth of this ray are composed of an upper part 

 apparently made of enamel and a lower part seemingly composed of dentine, 

 as will be shown later. 



The first man who ever published a figure of the curious jaw structures of 

 Aetohatus narinari was Hans Sloane, whose drawings, from volume xix of 

 the " Philosophical Transactions," published in the year 1697, are herein 

 reproduced as text-figure 7. Sloane calls this the "tongue" of a flat fish, 

 named Pastinaca marina, akin to the Thornback Ray of Great Britain, 

 and found in the waters of Jamaica. He compares this to the lower man- 

 dible in man, finds it composed of 19 bones (his figure shows 18) separated 

 by furrows. He confuses top and bottom of the jav/, calling No. 2 the 

 under side when it is the upper, and similarly for No. i, which is the under 

 side with all the cartilages removed, showing the spongy bases of the teeth 

 previously referred to. Numbers 3 to 12 show very clearly the relation 

 of the enamel and dentine in the individual teeth, and also the shape of 

 the teeth of the lower jaw. Numbers 13 and 14 of this figure are drawn 

 from fossil upper jaws of an Aetobatid sent Sloane from Maryland. These 

 earliest figures have yet to be improved upon. 



