KONGL. SV. VKT. AKADEMIENS HANDLlNGAIi. BANU. 22. N:0 7. 53 



How difficult it may be to give goocl characturistics tor distinguishitig thc two prc- 

 ceding spccius troni one another, I think they must be regarded as differeiit species, or at 

 least varieties, until their identity might happen to be proved by the examination of a 

 greater number of specimens in different stages of developement. On the other hand it 

 is easy enough to point out reliable characteristics for the specific distinction of Thau- 

 matops Lovéni. The comparatively small head, the length of the seventh pair of pe- 

 rivopoda, the breadth of the peduncles of uropoda, with their short rami make it easy to 

 recognize this species. 



The head is broader and deeper than the pera^on, and equals the length of the tirst 

 three pera3onal segments together. The foremost part of the head is rounded. From the 

 front of the head runs on each side along the loAver part of the head a row of about 

 tifteen small teeth to the hinder margin of the head, above the mouth-organs. Thcse teeth 

 are not placed on a crista, as in the preceding species, but rise directly from the surface 

 of the head, and are not visible when the animal is seen from above. On the under 

 side of the head there is no row of smaller teeth as in the preceding species. The under 

 and hinder margins of the head are longer than the upper. The length of the head is 

 20 mm., the breadth 24 ram., and the depth 25 mm. 



The eyes occupy the upper parts of the head, they are not contiguous, but separated 

 by a narrow strip of the surface of the head. The ocelli as in the preceding species. 



The first pair of (intennce (Pl. IV, fig. 3) are a little longer than half the length 

 of the head, tixed soraewhat below the denticulated row which runs round the head. The 

 peduncle consists of one joint, very narroAv at the base, constricted, forraing a neck, the 

 distal part wide, almost cylindrical. The flagellum is more than four times as long as 

 the peduncle, px'ismatic, feebly bent downwards; on the upper margin there are two ob- 

 tuse prominences, possibly hinting to a division of the flagellum into three joints, as is the 

 case in Guérin-Méneyille's specimen, according to his statement. No smaller terminal 

 joints are to be seen, the apex of the flagellum is provided with two minute hairs. Tlie 

 length of the antennas is 11 mm. 



The second i^air of antennce are represented by two spine-like tubercles on the under 

 side of the head just in front of the mouth-organs. 



The labrum is broad, the under margin almost straight, feebly emarginate in the 

 middle, not hirsute. 



The inandibles^) (Pl. IV, tig. 4 and 5). The stem is stout and robust, the outer 

 side curved, smooth, the molar tubercle is placed a little below the middle of the stem, 

 finely ciliated, the grinding surface with three rows of sharp denticles; the incisive pro- 

 cess is strongly denticulated, showing seven triangulär, sharp teeth, and one larger at the 

 inner corner; in the left mandible the appendicular process is armed witli four sharp teeth. 



The lahiuvL is hirsute, deeply bilobed, the under margins evenly rounded. 



The first -pair of maiulke (Pl. IV, tig. 6) consist of two laminas; the inner ur prin- 

 cipal lamina is broad at the base, the process is short, almost truncated at apex, armed 



*) 111 »Remarks on the genus Cysteosoma or Tliaumatops", p. 7, fig. 3, I described and figured the 

 apex of a mandible from the young specimen of Th. longipes; here above I give soine details of the låter examined 

 mandibles of the probably fuUgrown Th. Lovéni. 



