ARCTURUS. 363 



Milne Edwards) : 1. Arcturus Proper, containing Idotea 

 Baffini, and 2. Leacia, Johnston, containing Oniscus 

 longicornis, Sowerby (to which Dr. Johnston, regarding 

 it as undescribed both generically and specifically^ had 

 given the name of Leacia lacertosa). Mr. H. Goodsir, 

 however, considered the two sections as of generic rank, 

 and accordingly retained the name Leachia for the 

 British species. Until recently, a single British species 

 has only been recognized. The late lamented Harry 

 D. S. Goodsir, Surg., R.N., however, detected two 

 other species, of which he published descriptions and 

 figures in the 31st volume of the "Edinburgh New 

 Philosophical Journal." Living specimens of all these 

 three species were captured by Mr. Goodsir with the 

 dredge in deep water in the Frith of Forth, and in the 

 German Ocean, but all these were found to be rare in 

 consequence of their pelagic habitat. Having kept these 

 animals in glass jars of sea-water, with sand and coral- 

 lines, Mr. Goodsir was enabled to watch their habits 

 closely. Under these circumstances each individual will 

 select a branch of coralline, keeping that branch ex- 

 clusively to itself, and defending it with the greatest 

 vigour against all intruders. It fixes itself to its resting- 

 place by means of its true feet, which it seldom uses for 

 progression. When it falls to the bottom of the vessel, 

 it fixes its long-pointed antennae into the sand, and with 

 the assistance of the true feet drags and pushes itself 

 forward. This, however, may not be a natural mode of 

 progression, but may be adopted in consequence of the 

 artificial circumstances in which the animal is placed. 

 The ordinary and natural mode of progression of these 

 animals is swimming. It is amusing to see one of these 

 animals resting in an erect posture, on a branch of coral- 

 line, by means of its true feet, waving its body back- 



