734 PROCEEDINOS OF THE NA TTONAL MUSEUM. 



5. LAMPETRA MITSUKURII iHatta). 



Petromyzon hranchiaUs Ishikawa, Prel. Cat., 1897, p. 83, Sapporo, Hokkaido. 



Hatt.v, Lampreys of Japan, rivers of northern Japan (not of Linnwus). 



Lamiietra mUmhirii Hatta, Ms. ba.sed on Petromiizon hranchkdii< Ilatta, not of 

 Linnffu.*. 



Lmnpctra mitmkurii Jordax and Snyder, Proe. F. S. Xat. Mus.. 1900, p. o.'id ( hm 

 description; young specimens from Tokio and Lake Biwa referred to liy 

 error; thoj^e belong to L.japoniea): — Jordan &. Snyder, Catal. Fisli .Taiiau 

 1901. 



Supraoral lamina formino- a crescentic plate, shortei- tliau in Z. 

 japomea, the cusp at either end shorter and more obtuse; infraoral 

 lamina with about six blunt cusps, the outer ones much broader and 

 longer than the others; lateral teeth three on each side, each bicuspid 

 and blunt, two or three rows of simple teeth in front of supi-aoral 

 lamina: lips fringed. 



Dorsal tins connected, the tirst two-tifths to one-third height of sec- 

 ond, the connecting membrane of the two tins a])out one-third height 

 of first. Head li in first dorsal, aliout one-tenth longer than thorax: 

 gill openings, 7; head, 9 in total length; tail. 4: (>2 muscular impres- 

 sions between gill openings and vent. 



Color bluish-black, the bell}- white: tip of tail l)lackish: tins pale. 

 edged Avith darker. 



Rivers of Hokkaido, and Hondo north of Sendai and Niigata, gener- 

 ally common. Here described from eight specimens, one 5i, the 

 others 12 to 14 inches in length, obtained from the Ishikari River, at 

 Sapporo in Hokkaido. The smallest one has seven infraoral cusps 

 and the teeth are less developed. It agrees in all other regards with 

 the largest one. 



From the lampreys of southern Japan this species is at once dis- 

 tinguished by the united dorsals. 



This species is related to Lampetra wilderi of the eastern United 

 States, and still more closely to Lampetra p)laneri (Bloch) of Europe. 

 It will require actual comparison of specimens to separate it from the 

 latter, but our experience with other species in widely separated regions 

 shows that it is very hazardous to assume identity of species simply 

 ])ecause superficial and noncomparative descriptions indicate no differ- 

 ence. The Japanese species seems to reach a larger size and to have 

 higher tins than the European. 



Named for Professor Mitsukuri, of the Imperial University of Japan. 



