238 NEOTROPICAL PSELAPHIDAE 



SYRMOCERUS (Rafifray, 1897) 



Raffray (1897) (Arthmius) (1904, 1908, 1911) 



This is a Brazilian genus of five species having many structural affinities 

 with Arthmius. It was originally erected as a subgenus of the latter but has 

 been recognized as distinct since 1904. The genus is quite disparate from its 

 nearest ally, Syrbatus, by the key character. The three genera, Arthmius, 

 Syrbatus and Syrmocerus form one evolutional line within the neotropical 

 batrisines, in which Arthmius with many species and a wide range has entire 

 pronotal margins and no longitudinal sulci, Syrbatus with about one third as 

 many species and the lateral pronotal depressions expanded apically into longi- 

 tudinally developed sulci, and Syrmocerus with sharply incised lateral pronotal 

 margins, the incisure caused by the development of a shorter, more arcuate, 

 heavily pubescent sulcoid fovea. The last two genera are entirely South Amer- 

 ican, and Syrbatus with a range which includes Brazil, Paraguay, and Argen- 

 tina, seems less highly specialized than Syrmocerus with five species limited 

 as far as known to the Brazilian rain forest. 



The following key, based on the male sex, will separate the known species: 



Key to the Males of Syemocerus 



Antennal segment I normally developed, subobconical to subcylindri- 

 cal, with the apical angles mutually developed and regularly acute 2 



Antennal segment I very abnormally developed, with the mesio-apical 

 or internal angle formed as a long spine or greatly expanded 4 



2. Dorsal surface of head with an entire, broad, obtuse, median longi- 



tudinal carina and the surface entirely and roughly granulated; 2.8 



mm rugiceps 



Dorsal surface of head with a short median longitudinal carina which 

 crosses occiput and extends apically for a short distance on the pos- 

 terior part of the vertex; dorsal surface of head not roughly granu- 

 lated but the area of the antennal tubercles is coarsely punctate ... 3 



3. Antennal segment III quadrate; V longer than IV, VI, or VII; an- 



tennal tubercles flattened ; head tuberculated posterior and ventral 

 to the eyes; vertex with a median, transverse, arcuate tubercle; 



2.8 mm dama 



Antennal segment III elongate-obconical ; III, V, and VII longer than 

 IV or VI ; antennal tubercles tumid ; head not tuberculated on lateral 

 or ventral surface; vertex with a median, subconical, erect tubercle; 

 1.8 mm guarinus new species 



4. Antennal segment I with the mesio-apical angle extended apically into 



a conspicuous, flattened, sinuo-arcuate tooth which reaches the apex 



of the third antennal segment; 3 mm cervus 



Antennal segment I with the mesio-apical angle extended mesio-pos- 

 teriorly in an abrupt, apically rounded, lamellate plate, the axis of 



the plate being at right angles to the segmental axis ; 2.9 mm 



gazella 



