GARMAN: THE CHIMAEROIDS. 263 
have two pairs of teeth above and one pair below, like recent members of the 
group, but the dorsal spine is absent, the body is depressed, and the frontal 
tenaculum of the male is elongate styliform, much as the proboscis itself; and 
the Myriacanthidae have the dorsal spine, have dermal plates on the head, 
and have two pairs of teeth above and one pair and a single symphyseal tooth 
below. 
A number of features are possessed in common by the living forms, features 
by which they are closely linked together and by which they are readily dis- 
tinguished from their nearest allies of the Plagiostomia. The form of body or 
the general shape, the mandibular suspensorium, the teeth, the lateral system, 
the lack of shagreen, the erectile first dorsal, the frontal tenaculum, and the 
ventral tenacula of the males, the wide separation of hemispheres and optic 
lobes of the brain, the articulation of rostral cartilages; these go to distin- 
guish the Chismopnea from the Plagiostomia. For family characters depend- 
ence is placed on the differences in regard to the proboscis, on differences in 
the structure of the notochord, on differences in the claspers, and on differ- 
ences in the brain and in the lateral line. The generic and the specific sepa- 
rations are made by differences in the details of tritoral development, by the 
slighter variations in forms of rostra, or in the structure of claspers, by minor 
differences in the distribution of tke lateral line, in the lengths and shapes of 
- the fins, in colors, ete. 
The partial descriptions given below are introduced not as redescriptions 
but as additions to knowledge of several species, rare or not easily secured, to 
which references have been made in this paper. The lists of genera and 
species recognized herein are given under the classification. 
Harrioitta raleighana. 
Plate 2, Figs. 3-5; Plate 4, Fig. 1; Plate 5, Figs. 3-9. 
Harriotta raleighana Goode and Bean, 1894, Proc. U. S. Mus., xvii. 472, Plate XIX. 
Figs. 1-4. 
The authorities of the United States National Museum have kindly permitted 
examination of some of the types from which this genus and species were origi- 
nally described. In consequence it is possible to add some items to the data 
already published. Necessarily they are limited to external features, as the 
specimens could not be dissected. 
Specimen 35631, from the North Atlantic (Lat. 39° 12’ N.; Lon. 72° 3’ 
30” W.), at a depth of seven hundred and seven fathoms, is the original of 
Figs. 1 and 2 on Plate XIX. of Vol. xvii. of the Proceedings of the National 
Museum, 1894, or of Figs. 37 and 38 on Plate XI. of the Oceanic Ichthyology ; 
it has the following measurements: Total length, 15.5, head, 3.5, snout to vent, 
6.5, and snout to mouth, 2.5 inches. The individual is an immature male, too 
young to have acquired the frontal tenaculum, the ventral tenacula, or the 
