Oral cone more or less produced. Mandibles penetrating the cone up to its apex, 

 and having outside at the base a slender, generally bisetose palp. Maxillae with 

 the inner' lobe the larger. Anterior maxillipeds, as a rule, shorter and stouter 

 than the posterior, and having the basal joint imperfectly defined, terminal claw 

 uniarticulate or in some cases biarticulate; that of the posterior ones always 

 3-articulate. Natatory legs on the whole of normal structure. Last pair of legs 

 biarticulate, with the proximal joint laminar and in most cases imperfectly defined 

 from the segment, distal joint lamelliform, and extended laterally. 



Remarks. This family, established by Thorell, is here taken in a more 

 restricted sense than is done by that author, who comprised within it also the genus 

 Dyspontius, which ought to be referred to quite a distinct family. Nor does it 

 fully answer to the sub-family Asterocherince of Giesbrecht, as I have found it 

 necessary to remove the genus Acontiophorus in to a separate family. 



Gen. 17. ASGOmyzOIl, Thorell, 1859. 



Syii: Asterocheres, Boeck. 

 Cyclopicera, Brady (part). 

 Artotrogns. Brady (part). 



Generic Characters. Body pronouncedly depressed, with the anterior 

 division broad and expanded. Cephalic segment very large and having the 

 rostral prominence more or less distinctly defined and incurved. Penultimate 

 trunk-segment much smaller than the preceding one, and partly covered by it; last 

 segment still smaller, and firmly connected with the genital segment. Tail not 

 much prolonged, and composed in female of 3, in male of 4 segments; genital 

 segment in female considerably dilated, and having the lateral edges clothed with 

 stiff hairs; that of male still more tumefied, and provided at the end, on each 

 side, with a prominent triangular lobe carrying a spiniform seta. Caudal rami 

 comparatively short and without any seta on the outer edge ; apical setae of mode- 

 rate length, the 2 mediate ones being, as usual, the largest, and distinctly jointed 

 at the base. Anterior antennae slender and elongated, exhibiting a proximal, 

 somewhat thicker portion composed of 9 short articulations, and a much narrower, 

 linear distal portion; terminal part, as a rule, composed of 3 articulations, which 

 however in some cases may be more or less completely coalesced; same antennae 

 in male distinctly hinged. Posterior antennae with the penultimate joint almost as 

 long as the preceding one. Oral cone, as a rule, pyriform in shape, though in 

 some cases abruptly narrowed to form a slender straight siphonal tube. Man- 



