IDALIA. 579 



short, simply j3innate, forming a complete non-retractile 

 circle, fawn-coloured. The surrounding filamental appen- 

 dages, four on each side, tapering, short, the three anterior 

 distant from each other, the fourth and posterior very 

 close to, and shorter than the third. Caudal extremity 

 earinated. 



Coast of Northumberland, from the coralline region ; 

 discovered by the authors of the " J3ritish Nudibranchiate 

 Mollusca." 



2. I. iN.iiQUALis, Forbes. 



Plate Y. Y. fig. 4. 



Body oblong, flattened, but very thick, trun(;ate in 

 front, suddenly tapering, pointed behind. Back circum- 

 scribed, elevated with steep sides. Dorsal tentacula 

 linear, laminated ; tentacular appendages set well apart, 

 filiform, the anterior pair shortest, the lateral or posterior 

 pair very long, longer than the tentacula immediately in 

 front of which they are set. The animal when crawling 

 usually carries its tentacles obliquely reflexed, the anterior 

 appendages curved upwards, and the long ones directed 

 sideways and backwards. The branchiae are from seven to 

 nine in number, forming a complete and erect circle ; on 

 each side of them are five or six rather short, unequal 

 filamentous processes, the anterior ones approximated. 

 The general colour is grey, speckled with white, yellow, 

 and brown. An opaque yellow line runs down the centre 

 of the tail, with dots of the same colour on each side of it. 

 The sides of the back are specked with madder brown and 

 yellow. The branchial plumes are tipped with purplish 

 brown, and banded centrally with white. The length 

 of the bodv is rather more that half an inch. 



