458 REPOET OF CT3MMISSI0NER OF FISH AND FISHERIES. 



ure and migrate from one to another. Three species belonging to this 

 group were taken at the surface with the towing-nets. The Lerneans 

 are remarkable creatures. The females are generally very curious in 

 form and very much larger than the more active and less abnormal males, 

 and they are very low in structure, the reproductive system being enor- 

 mously developed at the expense of nearly all the other organs. They 

 live upon the exterior and gills of fishes, with the head deeply buried 

 in the flesh, and subsist by sucking the blood of their victims. The 

 Lernoionema radiatum (Plate VII, fig. 30) is very common ou the men- 

 haden, and is also found on the alewives. / 



There are many kinds of parasitic leeches. One of the most remark- 

 able is the BmnchiohdeUa Eavenelii, (Plate XVIII, fig. 89.) This genus 

 is peculiar in having broad, foliaceous, lobed or scolloped gills along 

 the sides of the body. The large species figured was found several times 

 on the large " sting-rays," several of them usually occurring together, 

 on a large spot which had become sore and much inflamed. by their re- 

 peated bites. It is a very active species. 



The Cystohranclms vividus is a much smaller and quite slender leech, 

 which has small, papilliform, whitish gills that alternately contract and 

 expand along the sides of the body, each surrounded by a semicircular 

 white spot. The colors are brownish or purplish, with three rows of 

 small white spots on the back. This species is frequent on the common 

 minnow, {Fundulus pisculentus,) in autumn and winter, and lives, both 

 in brackish water and fresh water. With the last, on the minnows, is 

 found another slender leech, destitute of gills ; this is the Iclitliyohdella 

 Fimdnli. It has, like the last, four ocelli. The color is pale green with 

 darker green and brown specks, often witli whitish transverse bands 

 anteriorly, and a white ring behind the head, at the constriction ; some- 

 times there is a narrow pale dorsal line. 



A long, slender, sub-cylindrical leech, the Pontohdella rapaxY., (Plate 

 XVIII, fig. 91,) is quite common on the upper side of the " summer- 

 flounder," {CJuvnopsetta ocellaris.) It is a very active species, dark olive 

 or brown in color, with a row of square or oblong whitish spots along- 

 each side ; the suckers are pale greenish white. The young are reddish 

 brown, without spots. 



A species of PontohdeUa was found adhering to Mysis Americana, 

 near New Haven, May 5, in three instances, but whether this be its nor- 

 mal habit is uncertain. 



The MalacohdcUa ohesa V. (Plate XVIII, fig. QO) is a large, stout, 

 yellowish white leech, often two inches long, which is quite common in 

 the branchial cavity of the "long clam," {Mya arenaria.) 



The MalacohdcUa mercenaria V. is another similar species, but smaller 

 and more slender, which lives in the same way in the " round clam " 

 {Vemis mercenaria.) 



The Myzohdella luyubris is a small leech, which lives on the " edible 

 crab ^^ {GalUnectes hastatus,) adhering to the soft membranes between 

 the joints and at the base of the legs. 



