322 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
the position in which the palp is carried, and the irregular outline of 
the fourth joint, it is often very difficult to make out the joints with 
certainty when viewed from above in a specimen mounted on a 
slide, as the appendage does not lie out flat. In such cases the only 
safe method is to get the palp into such a position that it may be 
seen laterally; then the presence of a complete ring in the chitin 
and the arrangement of muscles inside gives the certain criterion of 
a joint. It is probable that Professor Verrill mistook the appear¬ 
ance in the fourth joint for an articulation, and so counted eight 
joints instead of seven. 
A form with 7-jointed palpi would not come in the genus Ammo- 
thea as heretofore defined, since this included only those species 
with eight or nine joints in the palpi, nor would it be embraced in 
the genus as recently restricted by me (Cole, : 04 , p. 262) to forms 
with only eight joints. It seems, however, that the species under 
discussion so closely resembles typical Ammothea that it should 
properly be placed in that genus, which would then include forms 
with seven or eight joints in the palpi. According to Leach (’ 14 , p. 
33) the species (A. carolinensis) upon which he based the original 
description of the genus had 9-jointed palpi; but on the other hand 
he states that the chelifori (‘ mandibles ’) are 2-jointed, and dis¬ 
tinctly so figures them. In dividing the genus it thus became a 
question in which group carolinensis really belonged, and which 
group should therefore retain the original name. Several reasons 
have led me to retain in the genus Ammothea the species with 
2- jointed chelifori and 8-jointed palpi and to place those with 
3- jointed chelifori and 9-jointed palpi in a distinct genus, Ammo- 
thella. In the first place, although it is possible that Leach’s speci¬ 
men may represent an intermediate form, the differences are so con¬ 
stant in those species which are well known that it seems more prob¬ 
able he has made a miscount of the joints of the palpi — a matter 
which may happen at times, as mentioned above. The character of 
the chelifori seems much more reliable and these he distinctly de¬ 
scribes and figures with two joints. Furthermore, the next forms 
which were referred to the genus are well known species with 
2-jointed chelifori and 8-jointed palpi (c/*. Hodge, ’ 46 ) ; and, finally, 
the species with which the name Ammothella was first used, is one 
in which the chelifori have three joints and the palpi nine joints. 
As has been pointed out in other places, the name Achelia used 
