suture we will find posteriorly a larger plate (Fig. 3, d), which articulates on its inner side with another obliquely transverse plate (b), which also is conjoined on its inner side by another (c), and that too by another, and finally in the centre there is a small tooth, as it were. These plates are respectively the coxa, femur, tibia, tarsus, and the rudimentary metatarsæ (the central tooth) of the atrophied and misplaced appendages of the second cephalic subsegment. The tibia and tarsus are generally anchylosed together, but I have seen them separate. Conjoined and posterior to the coxa of the second cephalic subsegment we will find a large plate (a) articulating with the cephalic scutum by suture; this I take to be the primitive sternum and episternum of the third cephalic subsegment atrophied and fused together; to it the true maxilte are articulated. These consist each of, first an elongated crooked plate (the coxa) articulating with two plates, the exterior of which (the femur) is armed with a tubercle, as in the mandibles, posterior legs, &c.; the inner plate is the tibia; these two plates articulate at their distal end with a third, the tarsus and metatarsus coalescent, but with the line of their junction very apparent. The maxillæ I believe to be the appendages of the third cephalic subsegment. Just anterior to the primitive sternum of the first, and posterior to that of the third, are often found some small plates which I believe to be epimeral. But the largest of the latter is probably the episternum of the fourth cephalic subsegment, which is scarcely to be found elsewhere. Proceeding still posteriorly we come to the maxillary palpi (Fig. 4), which are possessed each of a distinct femur (f), tibia (x), and tarso-meta tarsal joint (m). They are the appendages of the fourth cephalic subsegment. Between them are two small plates, the lingua (Fig. 4, l), which I think are the primitive sterna, not episterna (as Mr. Newport believed), of the fourth cephalic subsegment. Posterior to the sterno-episternal plate of the third subsegment is a subtriangular plate, one of the episterna of the first basilar subsegment; interior to this is a large irregularly four-sided one, forming a portion of the palpus (Fig. 5, a); this is one of the primitive sterna of the first basilar subsegment; still within this is an elongated plate (e), the coxa of the palpus. With these two last the femur (b) of the palpus is articulated at its proximate end, while to its distal end is fitted the tibia (x), and to it the tarsus (m). The sterna and appendages of the second and third are very much coalesced and difficult to distinguish clearly; but I think that the dental lamina are probably the appendages of the second basilar subsegment, the
