of the Amazon Valley. 43 



broad and the haunches cylindrical, the suture is long and 

 widely gaping. When the suture is opened only a little at its 

 commencement near the rim of the socket, the acetabula are 

 termed by Leconte " angulated ;" but it is often very difficult 

 (for instance, in the genus Acanthoderes) to say when they 

 should be considered angulated and when round. 



This work, however, being almost confined to North American 

 productions, could only be a stepping-stone to the desideratum 

 of a sound general classification of the Longicorn family. M. 

 Thomson, in his Essay, adopts the system of Leconte with some 

 slight modifications, and applies it to the Cerambycides of the 

 whole world, for doing which his very large private collection 

 afforded great facilities. He institutes a great number of sub- 

 tribes, groups, and divisions, arranged in order under the tribes 

 of Latreille as modified by Leconte. This, therefore, is by far 

 the most considerable work that has yet appeared on the subject, 

 and might be expected to form the groundwork and guide which 

 I have alluded to as being the great desideratum in this family. 

 It is, however, disappointing in many respects, although con- 

 taining much that is very valuable, and forming, upon the whole, 

 a real advance in the science. The greatest objection that can 

 be made to it is that, although there seems at first sight to be 

 a just and well-digested classification, yet the diagnoses of his 

 groups and genera, when examined into, are found not to apply, 

 in most cases, to the majority of the insects they refer to. The 

 characters very often are too general and random, and do not, 

 in fact, serve to characterize at all. The more detailed characters 

 of the numerous new genera, however, are given in a much more 

 satisfactory manner. Part of this obscurity is owing to the in- 

 nate difficulties that the study of the group presents, as will be 

 mentioned presently. Very many of his groups are natural, and 

 will doubtless stand their ground, but they will mostly still re- 

 quire to be defined. In his fifth group of Lamiaires, viz. the 

 Oucideritse, he gives as diagnosis, " Frons apud d saepissime 

 armata. Tarsorum articulus ultimus longissimus.''^ These two 

 characters apply equally well to many of his thirteenth group, 

 Hypsiomitse — to several genera of the Apomecyuitae division of 

 his Saperditse {Trestonia, Trachysomus, &c.) — and partly to his 

 fifteenth group, Hippopsitse. Some features of his classification, 

 however, are very good. Thus, by means of the system adopted, 

 he has been able to ascertain that the curious South-east Asian 

 group, Tmesistemitse, are true Lamiaires, notwithstanding the 

 porrect direction of the head — a superficial and erroneous guide, 

 which has misled all previous authors. The Callidiitse approxi- 

 mated to the Spondylidse is also a good arrangement; and there 

 are many others of the same nature. He has done great service. 



