BY N. DE MIKLOUHO-MACLAY AND WILLIAM MACLEAY. 677 



with a yellow margin, which, however, does not run all round the 

 disc, but leaves the upper part of the same free. (1) The gill 

 openings of equal size. 



Tail, thick and stiff, with a medium blue line on the upper side, 

 and two lateral ones on the sides, half as long as the body. 



Dimensions of a (J : — 



From the upper margin of the disc to the end of tail... 541 mm. 

 „ „ „ „ to the lower border 



of the disc ... 335 mm, 



Dentition.— Th.Q teeth of D. marginipiymis are, at the first glance 

 of nearly the same shape and size in both jaws ; they are closely 

 ini|)acted. and present, as in other Trygonidoe, a kind of mosaic 

 pavement " symmetrically arranged." (Fig. 13.) Inspected more 

 closely, the teeth of each jaw consist of three portions — a 

 median and two lateral ones, which are more distinct in the lower 

 jaw, being divided from each other by a vertical row of teeth with 

 longer and more pointed cusps. (These two rows seem to be 

 characteristic of the species.) 



The number of rows of teeth and of teeth in each row, is nearly 

 the same in each jaw. (There are about 32 or 33 transversal rows 

 in each jaw, and from 10-13 teeth in the median vertical rows, 

 wliilst in the rows of the lateral portions from 6-8 only.) These 

 numbers being of course dependent upon the age, and very likely, 

 upon the sex of the specimen can not be regarded as characters 

 of the species. 



Each tooth has a rhomboidal base supporting a more or less 

 distinct median cusp directed backwards. (Fig. 14.) 



The cusps of the teeth of the lower jaw are more obtuse than in 

 the upper, with the exception of the already mentioned two 

 vertical rows which show the largest teeth of the lot with the 

 longest cusps. (Fig. 15.) 



Habitat : Pacific Ocean, near the Admiralty Islands. Native 

 names — Bai at Sorry and La at Andra (another Island on the 

 north-coast of the large Admiralty Islands but further east.) 



(1) Examination of Fig. 10 will give a better idea of the shape of the 

 mouth and nostrils than descriptions. 



