76 



praorbital bone is placed at anterolateral side of the frontal. The supraorbital sutures with 

 the frontal medially, and might be over the lateral ethmoid anteriorly. 

 In Phoxinus, the supraorbital is a small, elongated crescentic bone. However, it is relati- 

 vely shorter and broader in P. oreas and tennesseensis (TS 53 [1]; Fig.40F) than that in 

 other species of the genus in which the supraorbital bone is relatively elongated and slen- 

 der (TS 53 [0]; Fig.40D). Its position relative to the supraethmoid, frontal, and lateral eth- 

 moid also varies among the species. In P. phoxinus, neogaeus, and cumberlandensis, the 

 supraorbital bone is placed forward; almost half of the supraorbital bone is above the la- 

 teral ethmoid (TS 54[1]; Fig.40E). In other species of Phoxinus, however, the supraorbi- 

 tal is placed more posteriorly; it does not overlap the lateral ethmoid, or only a small 

 portion of the supraorbital bone overlaps the lateral ethmoid (TS 54[0]; Fig.40F). 

 In the outgroups, the supraorbital bone is elongated and slender; only a small portion of 

 the bone overlaps the lateral ethmoid. 



Infraorbital series (Fig.41A-H). Four or five paired plate-like bones are included in 

 the infraorbital series: infraorbitals 1, 2, 3, 4, and 5 (Fig.41A-H). In some species of Cy- 

 prinidae, infraorbital 5 is present as two small pieces (e.g., Luciobrama macrocephalus - 

 Howes 1978); in some species, however, infraorbital 5 is absent (e.g., Cyprinella - May- 

 den 1989). 



In cyprinids, infraorbital 1 (lacrymal) is the largest and the most anterior bone of the in- 

 fraorbital series. It is located lateral to the vomer, and medial to the maxilla. In Phoxinus, 

 infraorbital 1 (Fig.41A-H) does not directly articulate with any other bone dorsally and 

 dorsoposteriorly, but with infraorbital 2 ventroposteriorly. Infraorbital 1 bears a concavity 

 at its anterior margin and a process on its dorsal margin. An infraorbital canal runs through 

 the bone. In P. phoxinus infraorbital 1 is relatively short and broad, its anterior and 

 posterior margins bear a well-developed notch (TS 55[1]; Fig.41E). In other species of 

 the genus and in the outgroups, infraorbital 1 is relatively elongated and narrow, both the 

 anterior and posterior margins bear no notch or bears a very shallow notch (TS 55 [0]; 

 Fig.41H). 



Infraorbital 2 (Fig.41A-H) is an elongated rectangular bone. It articulates with infraorbi- 

 tal 1 anteriorly and infraorbital 3 posteriorly. Its anterior portion is slightly broader than 

 its posterior portion in Phoxinus. There is variation of the bone among the species of 

 Phoxinus. In P. cumberlandensis, infraorbital 2 is short and relatively broad, its length 

 (anterior to posterior) is less than two times of its width (ventral to dorsal), and the an- 

 terior portion is equal to the posterior one in width (TS 56[1]; Fig. 4 IB). The condition in 

 other species of Phoxinus are similar to the condition in the outgroups. The bone is elon- 

 gated and slender, with the length about three times of the width; its posterior portion is 

 slightly narrower than its anterior portion (TS 56[0]). 



Infraorbital 3 (Fig.41A-H) is the longest among all infraorbital bones, and occupies about 

 half of the total length of the infraorbital series. (However, infraorbital 4 is the longest 

 among the infraorbital bones in some cyprinids, such as Luciobrama macrocephalus - Ho- 

 wes 1978, Chen 1987c). It is crescent in shape, and articulates with infraorbital 2 anteri- 

 orly, and infraorbital 4 posteriorly. In P. neogaeus, cumberlandensis, issykkulensis, and 

 erythro gast er, infraorbital 3 is equal in width, i.e., the width of the bone does not change 



