THE GENEKA AND SPECIES OF SYMPHYLA. 11 



which probably also are a kind of sense-organs, and exist in 

 some and perhaps in all species of the genus. On the upper 

 side of most of the joints, the proximal ones excepted, is 

 generally found a very small organ with the branches men- 

 tioned, and at least in one species two organs of this kind. 

 In Scut, crassicornis, n. sp., and Scut, pauper at a, 

 n. sp., there is besides on the same joints near the upper 

 organs a single, rather thick, conical rod ; in other species 

 this rod is very slender, often not easily discernible from a 

 normal short seta, and in Scut, a n g u 1 o s a some slender sub- 

 cylindrical rods with the end acuminate are found together 

 with the fine setce mentioned above in advance of the central 

 whorl on the distal joints. The quality and number of all 

 these organs present at least sometimes, and probably always, 

 specific characters to a certain extent. Some points are 

 briefly mentioned in the descriptions below, but a more 

 detailed study than I was able to undertake is needed. 



In Scolopendrella notacantha, Gerv., I have observed 

 two organs of the striped sort on the end of the terminal 

 joint. In Scol. Isabellce organs of a very different kind 

 were present on the same surface, but these organs are so 

 small that an enlargement of 600 times is quite insufficient, 

 and I have been compelled to give up the searching for sense- 

 organs in species of the genus Scolopendrella. 



D. Dorsal Scuta. — The tergum belonging to the segment 

 bearing the first pair of legs is rather or very short, and 

 never developed as a real scutum like the following ones ; I 

 have therefore found it practical not to include it in the 

 sum of the scuta ; when in the descriptions of the species the 

 second scutum is mentioned I mean the second of the large, 

 real scuta. It is well known that in all Syinphyla the 

 number of such scuta is a little higher than that of the pairs 

 of legs. In Scutigerella they are very easy to count ; four- 

 teen scuta are present in all species ; they are sharply defined 

 on the sides and especially behind, where a scutum in 

 somewhat contracted specimens overlaps the most anterior 

 part of the following one. In a very extended specimen of 



