224 



Records of the Indian MuseiDn. 



[Vol. IX, 



(5) The upper ends of the lateral plates on opposite sides of an 



arm are not closely approximated, so that, in T. elegans, 

 there is a wide dorsal surface (or shallow furrow in a 

 spirit specimen) on the upper surface of the arms. In 

 other words, the arm is more quadrangular in section, 

 while in T. palmiferus , the approximation of the upper 

 ends of these plates makes the arm almost triangular 

 in section. (This point of difference only refers to the 

 proximal part of the arm — in the more distal parts the 

 arm remains flat below, while the dorsum and sides 

 form a continuous curve.) 



(6) The talons borne on the tentacle papillae (text- fig. 3) show 



no great difference. Those of T. palmiferus generally 

 show a fluted appearance, and the outlines of the con- 

 vex surface are different. 



I have been able to count six bifurcations of an arm in this 

 example. 



Though I do not think that the actual number of segments in 

 an arm and its branches are of any particular importance, for they 

 vary in different arms of the same specimen, yet I have included 

 some facts concerning them in the following table of measure- 

 ments, for comparison with other tables giving these particulars 

 in the case of T. palmiferus. 



Diameter of disc 



Vertical diameter of the bursal aperture 



Interval between a pair of bursal apertures 



Arms 



At base 



At 20th segment 



At 40th segment 



Breadth. 



13 mm. 

 6'7 mm. 

 4*0 mm. 



Length. 



From base to 1st bifurcation. . 90 to 112 mm. 



From ist to 2nd ,, .. 16 to 30 mm. 



From 2nd to 3rd ,, .. 15 to 17 mm. 



From 3rd to 4th ,, . . 14 to 17 mm. 



28 mm. 



2 mm. 



2*5 mm. 



Height. 



10 mm. 



7 mm. 



3'5 mm. 



No. of 

 segments. 



39 to 52 

 17 to 26 

 about 18 

 about 16 



Beyond the 4th bifurcation I have not unravelled the fine 

 branches to take measurements. 



REFERENCES. 



1. Agassiz, ly. . . 



2. Ludwig, H. . . 



Mem. Soc. des Sci. Nat. de Neu- 



chatel, vol. ii, 1839. 

 Zeit. Wiss. Zool., vol. 31, 1878. 



