590 ORDER A POD A. 



other, as far as I know, articulated animal. It is narrower, 

 in both a longitudinal and transverse plane, than the first 

 segment of the body, and is distinctly separated from it. 

 The lower part on the ventral side, is protuberant and 

 rounded. The summit is square, and is formed by the crest 

 of the labrum, with two large palpi (d, fig. 3), having nearly 

 the usual form amongst the Balaninse, and pointing towards 

 each other, but differently from in any other Cirripede, they 

 are united for their whole length to the labrum, and by 

 their extremities to each other. These parts together thus 

 form an arch or hood, within which stand the other 

 gnathites. The palpi are roughened by groups of very mi- 

 nute spines. At their bases they can be obscurely seen to 

 be separated from the rest of the mouth by an oblique 

 joining or articulation. The back of the mouth is formed 

 entirely of the labrum, which becomes narrow towards its 

 base : it is, from top to bottom, Tilths of an inch in height. 

 Within the hood formed by the palpi and labrum, a pair (c, 

 fig. 3), of very singular, compounded, mandibular organs pro- 

 ject freely, straight up, with their convex outer edges placed 

 parallel and close together, and their teeth pointing directly 

 from each other, so that they stand in a reversed position 

 compared with the jaws of all other cirripedes, and are 

 absolutely incapable of prehension. 



This compounded organ is singularly small compared 

 with the palpi and labrum: it is narrow, being about ^ths 

 of an inch in width, but is produced upwards, so that a 

 considerable length projects freely, and the rounded, pro- 

 perly external, margin, can be traced down for a length of 

 about girths of an inch. In a lateral view of the mouth, 

 the extreme tip of the mandibular organ could sometimes be 

 seen just projecting out of the hood. The mandibular organ, 

 when separated and carefully examined, presents the ap- 

 pearance, represented from a camera drawing, in (PL 24, 

 fig. 2): we here see three groups of teeth; of these the lower 

 set (c) consists of blunter teeth, placed more transversely, 

 and easily separated from the others, and altogether clearly 

 appears like a distinct organ. I do not feel nearly so sure 

 regarding the other two sets; my first impression was strongly 

 that they were distinct organs, closely united laterally to- 



