Mr. W. N. Lockington on American Alphei. 465 
or less irregular in form; the outer edge is either straightish, 
slightly convex, or undulating: s¢de arm-plates in the form of 
narrow ridges : arm-spines very short, covered with skin at 
the base, naked and minutely prickly at the tips; four in 
number, except near the disk, where a few plates are armed 
with five; the three upper ones are subequal, and only a little 
more than a millimetre in length, the lowermost one very 
minute, and situated in a line with the tentacle-pores; and a 
few of them towards the end of the rays are armed with a 
minute hook or double hook at the extremity. No tentacle- 
scale. Genital rime furnished with a distinct irregular elon- 
gate-oval plate at the outer extremity, extending a little 
beyond the actual opening into the disk. The general colour 
of the disk above is purplish brown, somewhat paler on the 
keels of the radial shields, considerably paler beneath ; arms 
light brown above and whitish below; the oral and aboral 
shields are of the same tint as the lower surface of the disk ; 
the skin covering the arm-spines is purplish brown, giving 
the arms a bordered aspect. 
Diameter of disk 25 millims., length of arm about 80, length 
of radial shields 10. 
LIUI.—Remarks on some new Alphei, with a Synopsis of the 
North-American Species. By W. N. LOCKINGTON. 
THe North-American species of the old genus Alpheus are 
now known to be very numerous, as many as sixteen having 
been found upon the Pacific coast, from Panama northwards, 
making a total of eighteen species from both coasts. 
Some kind of subdivision, in so numerous a group, 1s neces- 
sary for the sake of convenience ; and the presence or absence 
of arostrum and of ocular spines probably furnish characters 
as reliable as any. 
Dana, in 1852, availed himself of the absence of a rostrum, 
and the inversion of the hands, to separate the genus Beteus, 
which has been generally acknowledged until Kingsley, in 
his synopsis of North-American species of the genus Alpheus 
(Bull. U.S. Geol. & Geogr. Surv. vol. iv. no. 1, p. 189), pro- 
posed, on what appear to me to be insufficient grounds, to 
reunite them. 
In a large series of A. minus, Say, that author found many 
which wanted the rostrum; while in some other Alphez the 
dactylus works obliquely or horizontally, showing an approach 
to the characters of Beteus. 
