nANK OF CIRCULAR GROUPS. 345 



shell-fish, when properh' restricted, will be found groups 

 of the same value, that is, if we consider the Mollusca 

 as a class ; but if we view it, with Mr. MacLeay, as a 

 sub-kingdom, then they must be considered as classes. 



(42fi.) We shall illustrate the rank of Tribes from one 

 of the most perfect, and, now, the best-established groups 

 in zoology, namely, the order of Insessores, or perching 

 birds. This most extensive order has been correctly 

 stated* as the only one in the ornithological circle which 

 contains tribes, designated and characterised as follows : 

 — 1. Conirostres, with a conic bill, and pre-eminently 

 perchers. 2. Dentirostres, or perchers of prey, with 

 sharp claws, and living chiefly upon insects. 3. Fissi- 

 rostres, with large heads, flat bills, and weak feet, as the 

 swifts and swallows. 4. Tenuirostres , with small eyes 

 and mouth, and long bills, like the humming-birds. 

 And, lastly, 5. The Scansores, or climbers, which brings 

 on the woodpeckers, parrots, and cuckoos. These are the 

 only tribes, or groups between families and orders, to be 

 found in the class of birds. But in most of the orders 

 of the Ptilota, or winged insects, tribes are very preva- 

 lent. The lepidopterous order, for instance, has the five 

 tribes of Diurnes, or diurnal butterflies ; Sphingides, or 

 hawk-moths ; Bombycides, or silk moths ; Phalcenides, 

 or geometric moths ; and Noctuides, or night moths : 

 although, as Mr. Kirby truly remarks, the primary di- 

 vision of this order is into three; the three aberrant 

 tribes forming one circle. In the coleopterous order the 

 tribes are very large, of which we shall cite the Lamelli- 

 cornes {ScarabcBus Lin.), or herbiverous beetles, and 

 i\\e Prcedatores, or rapacious beetles (Chilopodomorpha 

 MacL.) as examples, to be hereafter verified. It is ques- 

 tionable whether tribes occur in the aberrant orders of 

 either the Annulosa, Mollusca, Radiata, or Acrita, any 

 more than they do in the aberrant orders of birds. At 

 all events we have not yet detected them. 



(427.) Families are comprehended under tribes, when 

 the latter exist; otherwise, as in the case of the Rasores, 

 * Linnsean Transactions. 



