The ?iatural History of the Frilled Shar\ 273 



Study of Table VIII reveals the fact that there is considerable variation in the 

 number of rows of teeth. For the largest fish but one ever taken (a female, 1910 mm. long), 

 CoUett has the lowest count, 11-0-12 above, and 10-1-10 below. The latter is the lowest 

 count for either jaw in any fish. The largest count (13-1-13 — 27 above) is found on our 

 specimen No. I, a female only 1350 mm. long, or 100 mm. shorter than the average of 58 

 measured fish. Jordan and Fowler's count (1903) is normal for the upper jaw, but 

 rather scant for the lower, being next lowest in rank to that for Collett's specimen but 

 agreeing in total count with Bertrand. 



The varying counts in the table, and particularly certain abnormalities shown only 

 partly therein, call for statement and discussion. Carman's first and erroneous count has 

 already been referred to. His figures in our table are those of his final and more accurate 

 count. He found one more row of teeth on each side on the upper than on the lower jaw, 

 but found one central row below and none above. Giinther had difEculty in getting the 

 exact count at the angle of the jaws. Collett's figures are consistent, but he added in a 

 footnote that "In the present specimen the second side row of the left lower jaw is ab- 

 normal, being double (with two closely adjoining rows, all the teeth in them being some- 

 what smaller than normal teeth)." In this connection it is a matter of regret that CoUett's 

 fine figure of the head and jaws in lateral view (our Figure 6, plate II) was not made of the 

 left side instead of the right. 



Mrs. Hawkes (1907) found the teeth in all her specimens (two in the Liverpool 

 University, and three in the British Museum) bilaterally symmetrical with no median row 

 in the lower jaw, but she added (presumably referring to the lower jaw) that "In every 

 specimen examined, however, there was a torsion of the left front row of teeth toward the 

 right side; and in one case this resulted in a median row of teeth as described by Carman, 

 but the total number of rows of teeth was still 52." Bertrand and Lozano found no such 

 abnormahties in their specimens, and their counts call for no comments. 



There are left our specimens, three adult fish listed elsewhere in our table of sizes, 

 and the head of a fourth adult kindly loaned from the zoological museum of Columbia 

 University. Our counts of the teeth in these vary so greatly among themselves and in 

 comparison with the specimens already considered, and the Columbia specimen has such a 

 marked abnormality, that it is necessary to go into details. 



Like other investigators, we have had much trouble in making counts, especially in 

 our specimens I, II, and III, in which the jaws had hardened in a closed position. By 

 distending each mouth as widely as possible, by focussing a light on the angle of the jaws 

 and by using a magnifying glass, and above all by much practice, we have finally obtained 

 counts which are found to be correct by repeated checkings. To count the very small 

 teeth in the crowded rows at the angle of the jaw, one must get in position to look down 

 the length of the row; failure to do this is probably one explanation for the divergent 

 counts recorded in Table VIII. 



In our first fish (a female, 1350 mm. long) there are 13 rows of teeth on each half' 

 jaw, upper and lower, plus a central row at the symphysis of the lower jaw, which gives 



