ACANTHOCEPHALA. 119 
et simillima, tibiis posticis superne distincte spinosis, articuloque quarto antennarum 
fulvescente differt.” The specimens figured are from Yucatan; and fig. 24 represents 
the male form described by Dallas as M. thoracicus. It will be noticed that in the 
specimen represented by fig. 19 the posterior angles of the pronotum are strongly 
angulated. This, however, exists in all the forms of the species, but is best seen in 
those specimens in which the pronotal surface has become somewhat raised, and is a 
character which, though faithfully portrayed by the artist, for these reasons possesses 
no distinctive value. 
Var. guatemalena. (Acanthocephala alata, Tab. X. figg. 14 & 15.) 
Q. Closely allied to A. declivis, but differs principally by the greater dilatation of the posterior tibie, which 
are rounded and not acutely truncated at apex. 
Long. 25-35 millim. 
Hab. Guatemaua, Teleman, La Tinta, Cerro Zunil, San Isidro, Las Mercedes 
(Champion). 
The varietal character only of this form is well shown by fig. 14, which represents a 
specimen in which the outer dilatation of the right and left posterior tibiee is seen to be 
asymmetrical ; the apex of the left tibia is also acutely truncated, whilst that of the 
right is rounded, a character otherwise constant in three specimens before me. The 
male resembles in all respects the same sex in A. declivis. 
Var. panamensis. (Tab. XI. figg. 223 & 239.) 
Allied to A. declivis, Say, but differs by the much greater dilatation of the posterior tibiw in both sexes, which 
in the female is greater than in typical forms of A. declvis and less than in var. guatemalena. 
Long. 32 millim. 
Hab. Panama (Boucard). 
It is possible that these two supposed varieties may prove to be local races; but at 
the present time I have neither seen a sufficient number of specimens, nor sufficient 
constancy in characters to warrant my forming that conclusion. Certainly the typical 
forms of the species do not seem to extend further south than Mexico; but, on the 
other hand, the increasing dilatation of the posterior tibie does not correlate with 
decreasing latitude in habitat, as the Panama variety is intermediate in that respect 
between the variety from Guatemala and the Mexican typical form. 
8. Acanthocephala subalata, n.sp. (Tab. XI. fig. 20.) 
3. Fuscous, faintly and obscurely clothed with ochraceous pubescence. Antenne with the first and second 
joints subequal, third shorter, remainder mutilated. Pronotum with the anterior third densely pubescent, 
lateral margins denticulated, lateral angles produced, with their apices subacute and their margins denti- 
culated ; posterior angles moderately produced on each side of base of scutellum. Apex of scutellum pale 
greenish. Membrane dark shining cupreous, of which the basal third is somewhat paler. Body beneath 
concolorous, excepting fore and intermediate trochanters, bases of femora, tibie, all the tarsi, and a large 
spot at odoriferous apertures, which are more or less dull ochraceous. 
Fore and intermediate femora with a row of small spines beneath; posterior femora much thickened, with a 
