120 On a Parasitic Copepod of the Clam. [February, 
the Copepoda parasitic on Mollusca with the exception of the 
Penella larve found on the gills of cuttlefishes, the Artotrogus 
from the egg-sacs of Doris, and certain species of Splanchno- 
trophus, which bore into the skin of nudibranchiates. 
Hitherto, so far as I have been able to determine, only three 
cases of Copepoda parasitic on lamellibranchiates have been re- 
corded, viz., Authessius solecurti Della Valle, on the external sur- 
face of Solecurtus strigilatus) Modtolicola insignis Aurivilius, 
from the gills of Modiola vulgaris and Mytilus edulis? and Pac- 
labius tumidus Kossmann, from the pericardium of Tridacna (Phil- 
ippines),? I have not had access to the description of the last- 
named form, which belongs to the Ergasilide, and, according to 
Aurivilius, shares the great development of the cephalothorax, 
the absence of appendages on the fifth segment and the long egg- 
sacs with the genus Ergasilus. The two other forms are closely 
related to Lichomolgus, and.apparently still more closely allied 
to each other, for a comparison of the figures shows that their 
most divergent characteristics, the mouth parts and the fifth pair 
of thoracic appendages, do not present greater differences than 
are to be met with in the range of the genus Lichomolgus.! 
Further investigation will show whether it is desirable to retain 
them in separate genera. 
It will appear from the following generic diagnosis of the clam 
parasite that it occupies a position intermediate between Licho- 
molgus and Ergasilus: i 
Myicola, n. g.—Cephalothorax of Q oblong, of oS pyriform, composed of six seg- 
ments, the last of which is reduced in size and carries a pair of uniramous appen- 
dages. Abdomen as in Lichomolgus, Anterior antennz of seven joints, posterior 
of four, robust, the basa? joint tumid, the terminal one converted into a single strong 
claw ; mandible with triangular base and several setose lobes. Maxilla as in Licho- 
molgus, First pair of maxillipedes robust, three-jointed, the basal joints tumid, the 
terminal one carrying two setose filaments. Second pair of maxillipedes adsent in 
Q , resembling those of Lichomolgus in g. Natatory feet as in Anthessius and 
Modiolicola, _ 
This genus approaches Ergasilus in the conformation of the 
posterior antenne and in the absence of the posterior maxilli- 
Della Valle. Sui coriceidi parassiti, e sull’anatomia del gen. Lichomolgus. 
Mitth. Zool. Stat. Neapel, 11, 102. 
2 Aurivilius. Bidrag till Kannedomen om Krustaceer som lefva hos Mollusker 
och Tunicater, pp. 9 and_39, Sep: imp: from ‘‘Oef: Kongl: Vet-Ak: Forh.,” 
Stockholm, 39 Arg. 
3 Kossmann. Zool. Ergebnisse, Leipz., 1877. 
tcf. Brady. Brit, Copepoda, Vol. 111. : 
