THE GENUS ANASPIDES. 797 



the grounds for this statement are neither specified nor obvious. Each of the thoracic 

 legs bears at its base an appendage about one-half as long as the limb itself, and nearly 

 twice as broad, bluntly pointed at the tip, and indistinctly divided into three joints. 

 Packard, in his preliminary communication, describes these as " breeding lamellae," 

 but in his later paper he withdraws this interpretation, and states that these appendages 

 are to be regarded as " endopodites." What is meant by this use of the term endopodite 

 we cannot understand, and the matter is made no clearer by Packard's reference to 

 the " large ovate-lanceolate endopodites " of Petalophthalmus, for these can be no other 

 than the brood-lamellae themselves. In Packard's figures, what is apparently the main 

 axis of the limb is lettered as the exopodite, but no explanation is given of this remark- 

 able departure from ordinary nomenclature. The position of these so-called " endopo- 

 dites " suggests that they correspond to the natatory exopodites of Schizopods, but they 

 seem to differ very strikingly in shape from the slender, many-jointed exopodites usual 

 in that group. An alternative hypothesis in regard to their homology is suggested 

 by the resemblance of these organs in Palseocaris to the epipodial lamellae of Anaspides, 

 and more particularly to those of the maxilliped. This suggestion is founded partly on 

 these considerations of size and appearance, further on the ground that a remarkable 

 agreement has been shown to exist between Palseocaris and Anaspides in regard to other 

 very important characters, and, lastly, on the ground that true exopods might very likely 

 have perished in the fossil were they, as it is not unreasonable to suppose they were, 

 similar either to those of the true Schizopods or of Anaspides itself; there can, indeed, 

 be no strong presumption of their absence from Palseocaris in view of the many small 

 and fragmentary structures that evidently lie entangled in this portion of the fossils. 

 On this view, the single articulation at the base of each gill-lamella in Anaspides might 

 conceivably be taken as the vestige of a segmentation formerly present in these organs, 

 and partially preserved in Palseocaris. 



The first five pairs of abdominal appendages in Palseocaris are powerful swimmerets, 

 consisting each of a stout peduncle carrying " probably two slender rami," though only 

 one is shown in the figure. The sixth pair form, w r ith the telson, the usual tail-fan 

 (fig. 15a). The outer plate or exopodite has a longitudinal median ridge, the homologue 

 of which is to be recognised in Anaspides, and as in that form a transvere suture crosses 

 the exopodite near the tip. The inner plate or endopodite is shorter than the outer, but 

 longer than the telson, which is rounded at the tip and edged with setae. Packard 

 states that " there are traces of a pair of abdominal legs to each of the seven segments," 

 but we may be permitted to doubt the existence of so extraordinary a deviation from 

 the ordinary structure of the Malacostraca. 



Particular interest attaches to the statement that the head of Palseocaris "is 

 apparently composed of two segments." In the original figure of Meek and Worthen 

 there is no trace of this, but in Packard's restoration a line running downwards and 

 backwards on the side of the cephalic region cuts off a wedge-shaped segment. The 

 direction of this line is very different from that which we have called the cervical groove 



