ACUTANGULUS.—NEOLEPTODESMUS. 179 
The two described species, both unknown to me, may be separated as follows :— 
a. Length 18 millim. Phallopod slender, curved, swollen at the base, ending in 
three longish down-bent subequal processes woe eee en coccineus. 
a’, Length 14 millim. Phallopod stouter, straighter, ending in three short processes, 
of which only one is sharply bent downwards. . . . 2. . . 1... neglectus. 
1. Acutangulus coccineus. 
Polydesmus (Tropisoma) coccineus, Humb. & Sauss. Rev. et Mag. Zool. (2) xxi. p. 152 (186)))*. 
Polydesmus (Strongylesoma) coccineus, Sauss. & Humb. Miss. Sci. Mex., Myr. p. 50, t. 1. fig. 12 
(1872) ?. 
Acutangulus coccineus, Attems, Denk. Akad. Wien, Ixvii. p. 409 (1899)*; Carl, Rev. Suisse Zool. 
xi. p. 560 (1903) *. 
Colour red, whitish or pink when dried. Body smooth or lightly striolated, vermiform, of equal width 
throughout. Head shining, with frontal suleus little marked. First tergal plate bordered, with straight 
posterior border, laterally pointed and triangular. eels of 2nd and 3rd segments directed a little 
backwards; the remaining keels small, forming a narrow ledge, their posterior angle lightly prolonged 
and dentiform, tending to become effaced from about the 12th segment backwards; those of the 19th 
almost absent. Pores just above the lateral edge, near the posterior end of the keels. Caudal process 
of 20th segment triangularly truncated. 
g. A little smaller, but with keels better developed. Phallopod slender; distal segment lightly arched, 
expanded at the base, hairy along its lower edge, ending in three subequal, up-turned processes, a proximal 
slender and pointed (seminal stile) and two distal a little longer and more sickle-shaped. 
Length 18 millim., width 2. 
Hab. Mexico, Orizaba (Sumichrast }~*), 
9. Acutangulus neglectus. 
Folydesmus (Strongylosoma) coccineus, var., Sauss. & Humb. Miss. Sci. Mex., Myr. p. 51 (1872) '. 
Acutangulus neglectus, Carl, Rev. Suisse Zool. xi. p. 560, t. 16. fig. 16 (19038) ”. 
Smaller than the preceding, but similar in form. and principally distinguishable by the structure of the 
phallopods, of which the distal segment is straighter, less swollen at the base, with the seminal fossa less 
circumscribed, more open distally, and with the three terminal branches much shorter; the seminal 
stile lies in the same direction as the main branch of the segment; the proximal of the two subsidiary 
branches is abruptly curved downwards, lamellate and constricted at the base (seen in profile), and the 
distal is short and somewhat toota-lke. 
Length 13-14 millim., width ? 
Hab. Mexico, Orizaba (Sumichrast +). 
‘This species was based upon some small examples mentioned by Humbert and 
Saussure, and found by Carl amongst those described by the former authors as 
Polydesmus (Strongylosoma) coccineus. 
NEOLEPTODESMUS. 
Neoleptodesmus, Carl, Kev. Suisse Zool. xi. p. 557 (1908) *. 
Resembling Leptodesmus in form and general characters, but differing in the structure of the phallopods. 
Antenne long and slender, Furst teryal plate as wide as the others, with rounded side-angles and 
2a2 
