Miscellanea Zoologica. 369 
turalists to classify them in one and the same genus, and it is suf- 
ficiently close to justify us in calling them Sea-spiders, were an En- 
glish name necessary for their identification. They are characte- 
rized by having a crustaceous slender body, not much thicker than 
the limbs, and which may aptly enough be compared to a short 
vertebral column, each segment representing a vertebra with its 
prominent lateral processes. This column is divided into five seg- 
ments only, which are so far anchylosed that their joints appear to 
admit of no motion upon one another, either to a side or perpendicu- 
larly : the anterior is rather the largest, and on its vertex there is 
a tubercle or small wart surmounted by four simple eyes placed in 
a square, but which are very difficult to detect in some of the spe- 
cies, if they are not actually wanting. I believe that this anterior 
segment is formed by the confluence of two a cranial and thoracic, 
and in the Pycnogonurn, the evidence of this division may be faint- 
ly traced. The cranial portion is sometimes lengthened out into the 
form of a neck and head, terminated with a short proboscis, but in 
others the proboscis springs directly from the truncate front into 
which it is inserted as in a socket. It is a tubular organ, of a crus- 
taceous texture, of extremely limited motion in a vertical direction, 
and with a simple round or trifid aperture at its apex, but in most 
of the genera the inferior side is divided into two equal halves by 
a longitudinal line or plain suture. * Generally at the base of this 
proboscis we find a pair of mandibles formed of two joints, the ulti- 
mate armed with a pair of claws or pincers, one of the claws only 
moveable ; and in one genus there is in addition to these a pair of 
filiform articulated organs, which have been named the palpi. All 
these belong to the cranial segment, if it is allowable to speak of 
this as distinct. The thorax consists of four segments, including the 
cranio-thoracic ; and each of them supports a single pair of legs, 
articulated with the protuberant sides of the segments. The legs 
are all alike in form, and calculated solely for creeping ; they are 
eight-jointed, t and the tarsus is provided with one or two strong 
* Savigny says that in the terminal mouth we can scarcely perceive some 
traces of a lip and jaws, and the manner in which the sentence is worded in- 
duces the belief that he could not discover any. Mem. sur les Anim. sans Vert, 
i. 55. The proboscis of a large species of Phoxichilus, from the Cape of 
Good Hope, appeared to be composed, says Latreille, of a lip, of a tonguelet, and 
of two jaws, the whole soldered together. Hence the palpi belong to the jaws. 
Cuvier, Reg. Anim. iv. 276. 
f The three basal joints constitute the coxce, the next the thigh, the two fol- 
lowing the tibia;, the other two the tarsus, but this nomenclature is objection- 
able in as far as it is founded on some very doubtful analogies between the parts 
so named, and the corresponding parts of vertebrate animals. 
