582 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



mouth, but never, to the author's knowledge, within the gill covers. 

 They are not as active as rapax, but upon occasion can move about 

 with equal speed and facilit}\ They live but a short time after being 

 taken from their host since they exhibit to a marked degree the per- 

 nicious habit of crawling up out of the water and remaining there 

 until dead. They are also very susceptible to a slight rise in tempera- 

 ture; Pickering and Dana say (p. 67) that "when the temperature 

 has been as high as 60° F., the} r have generally died in the course of 

 a short time." The author's experience has been similar, although no 

 actual temperature tests have been made. 



Being susceptible to so slight a rise it becomes extremely difficult 

 to handle them during the summer months, when most of the research 

 work is being done at the Marine Biological Laboratories. It is not 

 surprising, therefore, that so little has been ascertained in regard to 

 their habits and development, even though they are so common. 



The Museum collection includes the following: 



From the codfish (Gadus morhua) of Woods Hole and the imme- 

 diate vicinity four lots numbered 11618, and one each 12305, 12619, 

 12650, Ace. no. 19893, and the following collected by Vinal N. 

 Edwards, 1301, 1384, 1393, HIT, 1423, 1463, 1466, 1485. These lots 

 include something like 250 specimens. From codfish off the coast of 

 Maine, chiefly near Casco Bay, lots 8022, 8023, 8024, 8025, 12646, 

 12653, 12654, 12655, 12660, 12661, 12907, nearly 200 specimens more. 

 From codfish in Massachusetts Bay lots 12656, 12657, 12658. From 

 other localities, chiefly stations of the U. S. Bureau of Fisheries vessels 

 Albatross and Grampus, lots 16644, 12645, 12647, 12648, 12671, 12672, 

 12673, and W. 31. From the haddock (Melanogrammus seglefinus) 

 lots 12307, 12651, 12659, W. 25, W. 26, W. 41. From the hake 

 ( UrojAycis tenuis) lots 8026, 13203, W. 30. From the halibut (Hippo- 

 glossus hippoglossus) 12631. From the pollack (Pottachius^ virens) 

 W. 27, W. 28, W. 29. From the barn door skate {Raia Isevis) 858, 

 6162. From the surface 12908 and W. 32. Specimens of the chali- 

 mus of this species are included in lots W. 36 from the tomcod; W. 37 

 host unknown, and 8116 from fin of codfish. 



CALIGUS CHELIFER, new species. 

 Plate XI. 



Female. — Carapace ovate, a sixth to a quarter longer than wide, con- 

 siderably narrowed anteriorl} T . Frontal plates well defined; lunules 

 large, close together, nearly circular, and prominent (fig. 126). 



Posterior sinuses wide and nearly parallel; median lobe half the 

 entire width, projecting considerably, and contracted into a narrow 

 neck where it joins the free segment. 



Thoracic area two-thirds the width and one-half the length of the 

 carapace, subquadrilateral. Free thorax segment very short, a little 



