REPORT ON THE CEPHALOPODA. 



83 



the same region.^ One arm bears a supernumerary sucker in the largest specimen 

 (PI. III. fig. 2). 



Octopus tonganus, Hoyle (PL VIII. figs. 1, 2). 



1885. Octopus tonganus, Hoyle, Diagnoses I., p. 225. 

 1885. „ „ Hoyle, Prelim. Eep. I, p. 100. 



Habitat. — The Eeefs, Tongatabu. Three mutilated specimens, one $ , two ? . 



T7ie Body is rounded, depressed, and broader than long, with a marked but shallow 

 median groove on the ventral surface. The lyiantle-opening extends about one-third 

 round the circumference of the body, terminating nearer to the funnel than to the eye. 

 The siphon is short and conical, and extends rather more than halfway to the umbreUa- 

 margin. 



Tlie Head is small and the eyes prominent. 



The Arms are unequal, the order being 3, 2, 4, 1 ; on an average they are nearly 

 ten times as long as the body, and taper gradually to very fine points. The umhrella 

 is very small, and slightly narrower dorsally than laterally. The suckers are for the 

 most part small and closely packed ; the first four are arranged in a single row ; eight 

 smaU suckers surround the mouth, but there is no distinct lip. In the male there are 

 four large ones on each lateral arm opposite the margin of the umbrella, beyond which 

 they gradually diminish. The extremity of the hectocotylised arm is very minute (fig. 2). 



The Surface is in general smooth ; ' the back bears a few small papillge, but owing 

 to the compression of the specimens it is impossible to make out their exact number. 

 There are three minute cirri over each eye. 



The Colour is on the whole grey, paler below ; this is due to dark specks sprinkled 

 more or less closely over a cream-coloured ground. One specimen has a purplish patch 

 at either side of the mantle -opening. 



Dimensions? 

 Length, total, .... 

 End of body to mantle-margin, 

 End of body to eye. 



Length of extremity of hectocotylised arm, 

 Breadth of extremity of hectocotylised arm, 

 Diameter of largest sucker on lateral arm, 

 Diameter of largest sucker on dorsal arm, 



Length of frrst arm, 

 Length of second arm, 

 Length of third arm, 

 Length of fourth arm, 



1 Moll., Wilkes Expecl., 474. 



. 285 



mm. 



30 



„ 



32 



„ 



2 



,, 



0-75 



„ 



5 



„ 



3 



,, 



Eight. 



Left. 



150 mm. 



153 mm 



240 „ 



203 „ 



180 „ 



235 „ 



210 „ 



213 „ 



2 Taken from the male specimen. 



