1. PETKOMYZON. 505 



Petromyzon bicolor, Shaw, Zuol. v. 2. p. 203. 



pluinbeus, Shaw, I. c. 



Lampetra plaueri, Gnii/, Chondropi. p. 144. 



Developniunt : Aiif/. Midler, I. c. ; Max Schie/tzr, Die EntwlchlniK/^- 

 gescliichfc von Petromyzon planuri. Haark'in, 18oG, 4to. 



Dentition as in P.flwv'uttiUs, but the cusps are less prominent and 

 more obtuse. Tlie first and second dorsal are subcontiiiuous, al- 

 though separated by a deep notcli. Coloration immaculate. 



Ilivers of Europe and Western North America. 



a. Mature form. 



a~h. Stream three miles from Belfast. Presented bv R. Patterson, 

 Esq. 



c. Several examples. Firth of Forth. Purchased of Dr. Parnell. 



d. Many examples. Hawksfold (Sussex). Presented by 0. Salvin, 



Esq. — Caught end of April on spawning-ground. 



e. Many specimens illustrative of the metamorphosis. Berlin. 



From the Berlin Museum. 

 f-g. Tauber (Wiirtemberg). From the Stuttgart Collection. 

 h. Bavaria. Presented by Prof. v. Siebold. 

 i, Jc. Purchased. 



/3. Ammoccetes-form. 



a. Tweed. 



6. Eaton. From Leach's Collection. 



c-f. River Enz (Wiirtemberg). From the Stuttgart Collection. 

 g. River Blau (Wiirtemberg). From the Stuttgart Collection. 

 h. Numerous examples. Bavaria. From Dr. Cemminger's Collec- 

 tion. 

 i-k. Sardinia. Presented by Prof. BoneUi. 



4. Petromyzon ayresii. 



Petromyzon plumbeus, Ayres, Proc. L'aUf. Acad. Nut. Sc. 1854, p. 28 ; 

 Girdrd, U. S. Pac. R.R. Exped. Fish. p. ;{80 (not Shaw). 



There are only two teeth : the superior (maxillary) is low in tlie 

 middle, and elevated to a point at each end (as in P. Jluvi'ifi/i^ and 

 branchi(dis) ; the inferior (mandibulary) is serrated, having eight 

 or nine nearly oven points. The second dorsal is separated from the 

 first by an interspace, but continuous with the caudal. Anal portion 

 of the caudal scarcely conspicuous. Coloration uniform. 



San Francisco. 



Girard (/. c. p. 383) has described an Ammoco'tcs cibarius from 

 Puget's Sound ; it may be the larva of P. i>himhrus ; in its larval con- 

 dition it cannot be distinguislied from the Eurji)can A. branch iulis. 

 a. Numerous examples. British Columbia. Collected by the Boun- 

 dary Commission. 



The following species would appear to be the type of a distinct 



