ALBtTLIDJi]. 
67 
Mouth terminal, the mandible with truncated symphysis aud high 
coronoid region ; a single series of small, conical marginal teeth ; 
stouter and blunter teeth within the mouth, but apparently not on 
the parasphenoid. About 10 branchiostegal rays. Vertebrse about 
90 to 100 in total number, the centra short and deep, marked with 
delicate longitudinal ridges. Pelvic fins scarcely smaller than the 
pectorals, which are inserted high on the flank ; dorsal fin extending 
for more than half of the back ; anal fin short, opposed to or behind 
the posterior end of the dorsal; caudal fin deeply forked. Scales 
elliptical, not pectinated. 
The existing deep-sea genus Batliythrissa (A. Gunther, Ann. 
Mag. hlat. Hist. [4] vol. xx. 1877, p. 443) or Fterothrissus (P. Hil- 
gendorf, Leopoldina, pt. xiii. 1877, p. 127), is not yet clearly dis¬ 
tinguished from Istieus. Por description and figure, see A. Gunther, 
Hep. Deep-Sea Pishes, ‘ Challenger ’ Report, Zool. vol. xxii. (1887), 
p. 222, pi. Ivi. fig. A. 
Istieus grandisj Agassiz. 
1842-44. Istieus grandis, L. Agassiz, Poiss. Poss. vol. v. pt, i. p. 13, 
pt. ii. p. 92, pi. xviii. 
1842-44. Istieus microcephalus, L. Agassiz, ibid, pt, i. p. 13, pt. ii, 
p. 94, pi. xvii. [Imperfect fish ; Palaeontological Museum, 
Munich.] 
1842^4. Istieus macrocephcdus, L. Agassiz, ibid. pi. xvi. lower fig. 
[err ore). 
1858. Istieus qrandis, AV. von der Marck, Zeitschr. deutsch, geol. Ges. 
vol. X. p. 246. 
1858. Istieus microcephalus, AV. von der Marck, ibid. vol. x. p. 246. 
1863. Istieus macrocoelius, AV. von der Alarck, Palseontogr. vol. xi, 
p. 37, pi. iv. figs. 1-5. [New name., for I. grandis -1- I. micro¬ 
cephalus.'] 
1863. Istieus mesospondylus, AV. von der Marck, ibid. vol. xi. p. 38, 
pi. V. fig. 1. 
1863, Istieus macrocephalus, AV, von der Alarck, ibid, vol. xi. p. 39, 
pi. iv. fig. 6, pi. V. fig. 3 (errore). 
1873. Istieus macrocoelius, W. 'von der Alarck, ibid. vol. xxii. p. 59, 
pi. ii. fig. 2. 
1885. Istieus macrocoelius, AV. von der Alarck, ibid. vol. xxxi. p. 253. 
Type. Imperfect fish ; Paris Museum of Natural History. 
The type species, attaining a length of about 0*6. Length of 
head with opercular apparatus contained about two and a quarter 
times, maximum depth of trunk about three times in the length 
from the clavicle to the base of the caudal fin; width of caudal 
F 2 
