532 THE ENTOMOLOGIST. 



labrum ; and the second^ terminal, or claw-joint, which is 

 elbowed or bent back on the basal joint. To this definition 

 it may, perhaps, be reasonably objected that the articulated 

 or thumb portion of the claw is in reality a third joint. The 

 remaining limbs progressively increase in size and length 

 until the fifth pair, and, counting the moveable thumb as one, 

 all these have six joints. The sixth pair of limbs has seven 

 joints: the penultimate joint of this pair is differently con- 

 structed from the penultimate joint of the other pairs, since 

 it has five lamellae attached on its outer side ; the terminal 

 joint is very slender, and bears at its extremity the usual 

 didactyle claw, both the finger and thumb of which are 

 moveable. Following the sixth pair of legs is a small and 

 somewhat obcordate plate with a median suture, and again 

 beyond this are certain semi-membranous plates, the sutures 

 in which indicate joints, and these plates, covering the 

 breathing apparatus, are supposed, and with much reason, to 

 correspond with the swimming legs of ordinary crustaceans. 

 The basal joint or coxa of the claw-bearing limbs is produced 

 on its inner margin into a kind of flattened lobe, having its 

 edge sharply serrated or toothed, much in the san^e manner 

 as the maxillae of some Coleoptera, and evidently performing 

 the same function, namely, the laceration and comminution of 

 food : thus, without expressing the slightest judgment on the 

 honiologiies of these limbs and their constituent parts, it is 

 obvious that they are the analogues of the lacerating and 

 comminuting organs in the mouth of Coleoptera and decapod 

 Crustacea, ibr they perform exactly the same functions. The 

 comminuted food enters the pharynx or pharyngeal channel, 

 and passes forwards and upwards into the oesophagus, a 

 direction somewhat at variance with its course as usually 

 understood. I cannot express any surprise that entomo- 

 logists, finding in Limulusa structure so widely different from 

 that with which they were familiar in decapod and other 

 crustaceans, should have experienced some difficulty in 

 assigning appropriate names to the organs they observed, or 

 that there should be but slight accord in their views of the 

 homologues of the several organs. 



The first description which 1 would mention, but I by no 

 means consider it the best, is in the ' Regue Animal,' which I 

 believe was completed in 1815: it is cited by Savigny the 



