1. i-EXROMYZON. 505 



Petromyzon bicolor, Shaw, Zool. v. 2. p. 263. 



pliimbeus, Shaw, I. c. 



Larapetra planeri, Gray, Chondropt. p. 144. 



Development : Aitrj. Miiller, I. c. ; Max SchuHze, Die EntwicMutigs- 

 gcscliichte voti Petromyzon planeri. Haarlem, 1856, 4to. 



Dentition as in P.JIuviatiUs, but the cusps are less prominent and 

 more obtuse. The first and second dorsal are subcontinuous, al- 

 though separated by a deep notch. Coloration immaculate. 



Rivers of Europe and Western North America. 



a. Mature form. 



a-b. Stream three miles from Belfast. Presented by R. Patterson, 

 Esq. 



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



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



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



e. Many specimens illustrative of the metamorphosis. Berlin. 



Fxom the Berlin Museum. 

 f~(j. Tauber (Wiirtemberg). From the Stuttgart Collection. 

 A. Bavaria. Presented by Prof. v. Sicbold. 

 i, k. Purchased. 



/3. Aiv»ioc(etes-form. 



X. 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. Goniminger's CoUec- 



tiou. 

 i~k. Sardinia. Presented by Prof. Bonelli. 



4. Petromyzon ajrresii. 



Petromyzon plumbeus, Ai/res, Proc. Calif. Acad. Nat. Sc. 1854, j). 28 

 Girard, U. S. Pac. R.R. E.rpcd. Fish. p. .'380 (not Shaw). 



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

 middle, and elevated to a point at each end (as in P.JluvlatUis and 

 hntnchialis) ; the inferior (mandibulary) is serrated, having eight 

 or nine nearly even 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 {I. c. p. 383) has described an Ammoccetes cibatitis from 

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

 dition it cannot be distinguished from the European A. hranchialis. 

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

 dary Commission. 



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



