2. HT8TEE0CAHPUS. 251 



Amphistichiis heeitnanni, Girard, Proc.Ac. Nat. Sc. Phtlad. 1854, p. 135. 

 Ennichthys heermanni, Girard, I c. 1855, p. 323, and U. S. Paci^. P. 

 P. Exp. X. Fish. p. 199. pi. 38, pi. 26. fig. 9. 



D. ^. A. ^^. L. lat. 70. L. transv. 8/23. 



The middle dorsal spines are longer than the posterior and than 

 the soft dorsal. Scales on the cheek in five series, rather irregularly 

 disposed. The height of the body is contained twice and a fifth in 

 the total length (without caudal). Jaws nearly equal anteriorly ; 

 the maxillary extends nearly to below the middle of the eye. Lips 

 rather thin ; the fold of the lower continuous round the jaw. 



a. Adult. San Francisco. From the Boston Museum. 



16. Ditrema argenteum. 



Amphistichus argente us, ^ </«.<«. Am. Journ. 1854, p. 367, and Proc. Post. 



Soc. Nat. Hist. 1861, p. 131; Girard, Proc. Ac. Nat. Sc. Philad. 1854, 



pp. 141, 153; 1855, p. 323 ; and U.S. Pacif. P.P. Exp. x. Fishes, 



p. 201. pi. 39. 

 Mytilophagus fasciatus, (ribbons, Proc. Ac. Nat. Sc. Philad. 1854, p. 125. 

 Amphistichus simiHs, Girard, Proc. Ac. Nat. Sc. Philad. 1854, p. 135; 



1855, p. 323 ; and U.S. Pacif. P. P. Exp. x. Fishes, p. 203. pi. 36. 



figs. 5-9. 



D. ^. A. ^^. L. lat. 65. L. transv. 8/22. 



The middle dorsal spines are either nearly as long as, or somewhat 

 longer than, the posterior. Scales on the cheek in five series, some- 

 what irrcgidarly disposed. The height of the body is contained twice 

 and a fourth in the total length (without caudal). Jaws equal an- 

 teriorly ; the maxillary extends to below the centre of the orbit. 

 Lips thin ; the fold of the lower interrupted in the middle. 



a. Adult. San Francisco. From the Boston Museum. 



2. HYSTEROCARPUS. 



Ilysterocarjius, Gibbons, Proc. Acad. Nat. Sc. Philad. 1854, p. 124. 



Body compressed, oblong, covered with scales of moderate size ; 

 mouth rather small ; teeth conical, in a single series. One dorsal 

 fin, ^ith sixteen to eighteen spines. Anal with three spines and 

 numerous rays. Intestinal tract short, with two circumvolutions. 



Coast of California, entering fresh waters. 



1. Hysterocarpus traskii. 



Gibbon.% Proc. Acad. Nat. Sc. Philad. 1854, pp. 105, 124 ; Girard, ibid. 

 1856, p. 136, and U.S. Pacif. P. P. Exp. x. Fishes, p. 190. pi. 26. 

 fig. 14 (embr.). 



,D.;-&^ A., -A.,. L.lat. . L. transv. jg-,. 



The middle dorsal sjnncs are longer than the posterior. Scales 

 on the check in three series. The height of the body is one-third 

 of the total length (with the caudal). Jaws subcqual anteriorly; 

 lips rather thin, the fold of the lower continuous roimd the jaw. 



California. 



