294 CLAUS^ ON THE 



case is constituted of a labium and labrum, which surrounds 

 the oral orifice as a sort of groove^ we find four pairs of 

 members in the piercers, the pair of palpi and the small and 

 large jaw -feet. But the homology of these parts with those 

 in Nicothoe can the less admit of doubt, since the whole divi- 

 sion of the body foliovA's the same law, and the number also 

 of the antennse and thoracic feet in the groups above named 

 corresponds. The morphological peculiarities, which distin- 

 guish these families of parasites from the Cyclopidse, are 

 limited to the incompleteness in the number of abdominal 

 segments, and the shield-like shape of the thoracic carapace.^ 

 In the Dichelestiniinse, also, we meet with the same form and 

 development of the oral armature, and may be satisfied of the 

 existence of a similar degree of segmentation, inasmuch as 

 the abdomen may be seen to become gradually more and 

 more abbreviated {Lamproglene, Krdyeria).-\ But in this 

 family we may perceive still another retrogi'cssion. The 

 arrest in the morphological completion, if I may be al- 

 lowed to use such a term, is no longer limited to the abdo- 

 men, but invades the thorax, whose segments in Dichelestium, 

 though still, it is true, distinct, nevertheless are deficient in 

 the last pair of members, or, in Lernanthropus, are even fused 

 together into a continuous division of the body, sharply de- 

 fined from the interior part of the cephalo-thorax, and on 

 which the two first thoracic feet are supported in the form of 

 two branched swimming- feet ; whilst the two last are 

 elongated into sacciform eminences. 



In Clavella, lastly, a genus which has hitherto been ad- 

 mitted into the family of the Chondracanihee, although in the 

 oral armature it corresponds with Dichelestium, the last two 

 pairs of limbs are entu'ely wanting on the thorax ; and in 

 this instance all the thoracic somites are fused together, only 

 the two first rings of the thorax, which are furnished with pairs 

 of feet, being separated from the succeeding ones by a con- 

 striction. Hence the abdomen appears to be completely 

 aborted. 



With respect to the family of Chondracanth(B,X we have on 

 a former occasion referred to the genus Chondr acanthus, from 



* The numerous processes and appendages on the cephalo-thoracic 

 portions of the CaUgince^ &c., which formerly led me to conclude that the 

 antennae and oral members were subdivided into a ^reat manv lateral and 

 median pieces, are, for the most part, to be referred to chitiiious processes 

 of the carapace. 



f Vide E-athke on Dichelestium sturionis, as well as my " Observations oil 

 Kwi/eriri, Lenia?i(hropus, Clavella." 



X The other forms included in this family appear almost all to belong to 

 other groups. 



