THE HORNY SKELETON. 237 



the Orthoptern is found in the mole cricket (Gri/llottilpa vulgaris). In 

 the prothorax (PI. XI. No. 1. f. 1 3), which is formed of a very 

 large, hard, bellied pronotum (A) and a very narrow, small, keel-shaped 

 prosternum (B), we observe a large horny partition (c), which de- 

 scends from the central line of the pronotum and spreads forward in 

 two furcating processes (E, E) ; to these . processes two others attach 

 themselves, which originate from the upper margin of the aperture of 

 the neck, distend themselves in an arch downwards, and posteriorly, 

 and thus encounter the fork of the central ridge. And thence where 

 these processes join the furcate process the prosternum, which ante- 

 riorly is formed like a T, unites itself to them with its two branches, 

 and thus closes the anterior aperture of the prothorax. Posteriorly 

 two other processes originate from the central line (F, F), which de- 

 scend downwards, bend there towards each other, and join the posterior 

 extremity of the prosternum (*) ; at the same time each gives off a 

 hook which is directed upwards and backwards, and between these a 

 single horny bone lies (H), which stands in connection with them by 

 means of muscles (* *), and upon which the large pharynx rests. 

 Beneath this bone runs the nervous cord, encompassed by the posterior 

 shanks of the central ridge. The skeleton of the meso- and meta- 

 thorax is much smaller. Two processes descend from the scapulae 

 (PL XI. No. 1. f. 4 and 8. D, D.) and unite together beneath, at the 

 central line of the mesosternum (the same, E). From the point of 

 union there arises a short dagger-shaped process (the same, 5), which 

 is barbed on each side at its base, and proceeds nearly to the end of the 

 metasternum. This point is, as it were, the true breast-bone, to which 

 the muscles are attached, and upon it the intestinal canal rests. From 

 the anterior margin of the metanotum the small mesophragma ori- 

 ginates, and which is perforated by a hole (the same, 7- a), through 

 which the aorta passes, and besides there comes from the suture of the 

 metasternum and the pleura a clavate ridge, prolonged internally at its 

 anterior end into a pointed spine. 



Some of the Neiiroptera are very similar in structure to the grass- 

 hoppers, at least I found in the Termites just such horny arches upon 

 each of the three thoracic segments as covers for the nervous cord, and 

 horny ridges which separate the muscles from each other on the inner 

 surface of the pleurae. 



The most perfect internal skeleton of all however is found in the 



