396 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 09 



The conspicuous rostrum of Paranthessiiis is bent downward and 

 backward as a strong, pointed beak or hook, and, from the ar- 

 rangement of the supporting structures, obviously enjoys consider- 

 able freedom of movement. It thus becomes an important prehensile 

 structure in this genus. The chitinous bars and articulating masses 

 on the ventral surface of the head which support the rostrum include 

 in close association bars that are related to the bases of the antennules 

 and antennae. Running backward in the midline as far as the upper 

 lip is a broad straplike plate of chitin which, at its anterior end, is 

 rounded to form a very mobile articulation with the beak proper (fig. 

 34, F) . Curiously, Scott and Scott (1892) in their description of Lich- 

 omolgus agilis Scott (not Leydig) \=Paranthessius rostratus 

 (Canu)] interpreted the rostrum as a "short trumpet-shaped siphon, 

 capable of being extended or depressed * * *" Canu, in his mon- 

 ograph, illustrated the rostrum very well (Canu, 1892, pi. 24, fig. 3). 



The antennules are 7-segmented. The third segment is usually the 

 shortest; often it exhibits a great tendency to fusion with the adjacent 

 segments. An apparent trend is the stressing of the articulation 

 between segments 4 and 5, with the formation of a basal group (actually 

 inflated in some species) and with the terminal segments arranged 

 as a slenderer, more freely movable unit. 



The antennae are 4-segmented and there is a highly complicated 

 articulation with the ventral surface of the head. In some dissections 

 a considerable mass of the articulating region may come free with the 

 aj)pendage, suggesting a fifth, basal segment. In the descriptions of 

 various of the species a 5-segmented antenna is mentioned or depicted, 

 and I suggest that this interpretation is due to such an artifact. The 

 four terminal segments are similar, in any case. The first (basal) seg- 

 ment is short; the second is the longest of all, frequently somewhat 

 flattened in a plane parallel to the body axis (in the normal orienta- 

 tion of the appendage) and at the same time expanded mediolaterally. 

 The arrangement and ornamentation of the two terminal segments 

 follow various trends, as has been described above. 



The original description of Paranthessius Claus, 1889, was based 

 upon one of the most aberrant representatives of the genus, and as a 

 result, to the present, no satisfactory, complete resolution of the sub- 

 sequent multiplication of synonyms has been brought forward. 



The lichomolgid nature of Paranthessius was emphasized by its au- 

 thor, and very properly so, since, as has been pointed out above, ref- 

 erence to the amplified characters of the genus will show it to exhibit 

 in most fundamental arrangement the defining structures of this much- 

 abused family. A "Lichomolgus-like" body shape is typical of Par- 

 anthessius in Claus' sense. Further characters of his definition to 

 which we must still adliere would be the rostrum, antennule, antenna 



