Description of the Argulus Catostomi. 307 



In endeavoring to demonstrate, in the Argulus, the eleven pairs of 

 parts or organs which are commonly found posterior to the antennae, 

 in all the Crustacea, we proceed thus : — as reckoned above, there 

 are, including the tail, six pairs of branchial members ; next, two 

 pairs of prehensile, considering the suction legs as such ; then, two 

 pairs of maxillae ; and lastly, a pair of mandibles transformed into 

 the siphon. The bony arch, situated on the medial line, is not un- 

 like the bony wall which in other Crustacea forms the anterior bor- 

 der of the buccal aperture. 



J. V. Thompson, the author of many curious discoveries con- 

 cerning the metamorphosis of the Crustacea, has published* a short 

 notice of an anomalous parasite which he names Sacculina Carcini, 

 found by him on the Carcinus Manas. This parasite he considers 

 identical with the Argulus armiger of MUller, figured by Slab- 

 ber in plate 6 of his JVatuurTiundige Verlustigingen, (Haarlem, 

 1769-78) — a species we cannot find recognized in any work since 

 the time of Muller, except in the Encyclopedie Methodique, {Jn- 

 sectes, Art. Argule.) Mr. T. has not seen it in the mature state, 

 and it is therefore at present impossible to ascertain its relations to 

 the A. foliaceus or A. Catostomi. The larve appears to be totally 

 destitute of all organs of manducation. We hope to hear further 

 respecting so remarkable an animal. 



The buccal apparatus of the Pandarus alatus-f has, as from its sim- 

 ilarity of habits might be expected, some resemblance to that of the 

 Argulus, but the siphon when at rest, lies in a reverse direction. 

 An extended comparison between the trophi of these two genera, 

 would be of great interest. 



We are well aware that the foregoing account of the Argulus Ca- 

 tostomi is not complete. Many particulars of its habits and meta- 

 morphoses, together with many important details of anatomy are yet 

 to be discovered. Some of these deficiencies we hope to supply at 

 a future day. 

 New Haven, Conn., October, 1836. 



EXPLANATION OF THE PLATE. 



Fig. 1. Under view of the Argulus Catostomi. Seminal pouches r, r, 

 Fig. 2. Posterior branch of the first pair of antennas. 

 Fig. 3. Ternaination of the second pair of antennae. 



* Entomological Magazine, (8vo. London,) Vol. 3, p. 452 — 456. April, 1836. 

 t Described and figured by H. Milne Edwards, in Annales dea Sciences Natu- 

 relies, (Svo. Paris,) tome 28, p. 78—86, and plate 8. 



