Mr. T. Bell 07i the Leucosiadse. 361 



to the composition, as to render the whole equally capable of being 

 moulded into candles/ The truth of this statement I have myself 

 verified. 



"5. It has been stated by Dr. Macgowan (Journal of Horticult. 

 Soc. of India, vol. vii. p. 164), that the annual produce of the Insect- 

 wax in China is not far from £400,000 ; and when we consider the 

 very small quantity yielded by an individual insect, whether the 

 Coccus Pela or the Flata litnbata, it would appear probable that the 

 substance may be obtained from several insects, of which no doubt 

 the Coccus Pcla is one, and probably the Flata limbata is another." 



The paper was illustrated by specimens of the insect in its natural 

 state adhering to the leaf, and also by numerous preparations, 

 illustrative of the microscopic appearances and chemical relations, of 

 the waxy matter both of the Coccus Pela and Flata limbata. The 

 specimens of the Flata limbata adhering to the leaf have since been 

 deposited in the Museum of the Royal Gardens at Kew. Micro- 

 scopical delineations of appearances seen in the secretions both of 

 Flata limbata and of Coccus Pela, and of the spiral threads and white 

 hairs of the pupa oi Flata limbata, also accompanied the papepJi-'Oi^ofi 



^^' •"?ui'^¥$^Thomas Bell, Esq., President, in the Chair.^^,^."''^^^^ 



Read the first of a Series of Memoirs, entitled " Horse Carcino- 

 logicse, or Notices of Crustacea. I. A Monograph of the Leuco- 

 siadce, with observations on the relations, structure, habits and dis- 

 tribution of the family, a revision of the generic characters, and 

 descriptions of new genera and species." By Thomas Bell, Esq., 

 V.P.R.S., Pres. L.S. 



The author commences this paper with remarks on the distinct 

 limitation of the Leucosiadce, and the absence of any obvious osculant 

 forms by which to associate them closely with neighbouring groups 

 of the Oxystomata, and the no less striking want of any distinct re- 

 presentation of this family within the limits of other members of 

 the same great group. He refers, however, to a probable affinity in 

 the structure of the type of the Pinnotheridce, which has hitherto 

 been overlooked. The apparent approximation of the genus Oreo- 

 phorus to the Calappadce is also suggested, and a corresponding 

 tendency to a lateral expansion of the carapace pointed out in the 

 genera Lithadia, Nursia, Phlyxia and Ebalia. 



The history of the progressive knowledge of the family from its 

 first detection by Fabricius as a distinct group is then given. The 

 author enters at some length into the consideration of the nature of 

 specific characters in general, and the necessity of adopting such as 

 are tangible and certain ; and after deprecating the use of such as are 

 merely comparative between different species, he urges the import- 

 ance of giving, in all cases when a new species is described, such a 

 definition as shall point out as briefly as may consist with clearness 

 and certainty the points of distinction from all those which are 

 already known, and a description so full as to enable the future ob- 

 server to ascertain whether any individual afterwards examined is 



