77 



with the tips of the pectorals ; their height equals twice the length 

 of the central rajs of the anal. 



Caudal fin somewhat deeply forked, the height of the central 

 rays being but little over half that of the external, which latter is 

 about equal to the length of the head. 



D. V. 1-9, A 1-22, V. 1-5, P. 1-14, C. 10, 1, 8, 8, 1, 12. 



Of this species but a single specimen, six and one-fourth inches 

 in length, has yet been obtained. It was brought into the market 

 in this city, in company with other " smelts." It is a strongly 

 marked species, entirely distinct from the other two so common 

 here — A. caUforniensis (Grd.) and A. qffinis (Ayres). Accord- 

 ing to the divisions proposed by Girard, (Proc. Acad. Nat. Sci. VII. 

 1854) this would be a true BasilicJiiliys, and would take the name 

 B. tenuis^ but I can see no propriety in such a separation. A 

 trifling difference in the length of the upper and lower jaw, with 

 no other distinguishing features whatever, is certainly a very slight 

 basis for constituting three genera ; and though there may perhaps 

 be reason in dividing Aiherinopsis from Atherina, (though even 

 that is doubtful) there is, in my judgment, no question that Basil- 

 ichthys and Heterognathus can have no generic rank. The entirely 

 artificial nature of the arrangement is well shown in the fact that 

 A. tenuis is much more nearly allied to A. caUforniensis than it is 

 to Basiliclithysmicrolepidotiis^ (Grd.) the Chilian species, on which 

 the proposed division Avas based. The conical form of the head is 

 as fully marked in A. caUforniensis and A. aj/biis as in B. micro- 

 lepidotus or A. tenuis. 



November 5, 1860. 

 President in the Chair. 



Dr. Ayres read the following descriptions : 



JoJmius nohiUs, (Ayres) Fig. 20. — Form elongated ; dorsal 

 and ventral outlines gracefully and nearly evenly arched ; trans- 

 verse section elliptical, somewhat compressed ; head pointed, the 

 lower jaw a httle longer than the upper ; head in the adult fish con- 

 stituting a little less than one-fourth of the entire length, being 

 about equal to the greatest depth ; depth of the peduncle of the 

 tail not quite one-third of the greatest depth. 



Scales soft, rather small, not conspicuous, covering the body and 

 head, and extending on the pectoral, ventral and caudal fins ; scales 

 quadrangular, deeper than long ; those on the head smaller than 

 those on the body. 



Troc. Cal. Acad. Mat. Sci. g 



