SL. I have not seen the larvae of Aovcyhpsetta, 

 Gastrofsetta^ or Hippoglossina, but an ilhistration 

 of a 5.7-mm. SL Hiffoglossina oblotigus by Perl- 

 mutter (1939) ; and illustrations of a 6.5-mm. spec- 

 imen and a larger one by Agassiz, (1879, plate 9, 

 figs. 4 and 5) do not show a left side pelvic fin. The 

 pelvic fins of H. oblongvs appear very much later 

 than do the dorsal and anal fins (Agassiz, 1879). 



At 5 mm. SL Syaciiim, Cyclopsetta, Githarich- 

 thys, and Etropus have a well-developed pelvic fin 

 on the left side. The left side fin base appears at 2 

 to 3 mm. SL and is better developed than the right 

 side base, which develops later. 



I do not know at what size the pelvic fin bases 

 first appear in Engyophrys, Trichopsetta^ or Mon- 

 olene (I have assigned larvae exceeding 8 mm. SL 

 with well-developed pelvic fin bases to Engyoph^ys 

 and Monohne) . The origin of the left side fin base 

 of adults is adjacent to the cleithrum or slightly 

 anterior to it in Engyophrys, Trichopsetta, and 

 Monolene, but the origin of the right side fin base 

 is slightly posterior to the cleithrum. 



The origins of the left and the right side pelvic 

 fin base are posterior to the cleithrum in Para- 

 lichthys, Aneylopsetta, Gastropsetta, Hippoglos- 

 sina, Syacium^ Cyclopsetta, Citharichthys, and 

 Etropus. In Bothus and Chascanopsetta the origin 

 of the left side pelvic fin base is on the urohyal, 

 which is well in advance of the cleithrum. The 

 right side fin base of Bothus and Chascanopsetta 

 is short, and its origin is well posterior to the 

 cleithrum. 



CAUDAL OSTEOLOGY 



From late stage larvae to adults, the bothids 

 show a correlation between caudal Osteology and 

 position of the pelvic fui bases (table 1). Species 

 of Paralichthys, Ancylopsetta, Gasfropsetta, and 

 Hippoglossina have the dorsalmost principal cau- 

 dal fin ray associated with an epural ; the ventral- 

 most principal caudal fin ray has a spur associated 

 with it, and it is associated with the haemal spine 

 of the penultimate vertebra. The count of principal 

 caudal fin rays in this group, starting with the 

 epural and ending with the haemal spine of the 

 penultimate vertebra, is 1-2-6-4-3-1 or 1-2-6-5- 

 2-1 in Paralichthys. In these genera neither of the 

 plevic fin bases is on the median line and the origins 

 of both pelvic fin bases are well behind the clei- 

 thrum. 



Species of Syacium, Cyclopsetta, Citharichthys, 

 and Etropus have all 17 principal caudal fin rays 

 associated with the four hypural elements. The 

 dorsal-to-ventral count of principal caudal fin rays 

 on each hypural is 4-5-4-4. In these genera the left 

 side pelvic fin base is on the median line, and its 

 origin is well behind the cleithrum. 



Table 1. — Four generic groups which show a relation be- 

 tween the origins of the pelvic fin bases and number of 

 principal caudal fin rays associated with caudal elements 



lAsterlsks Indicate the genera for which I have no Identified larvae] 



Species of Engyophrys, Trichopsetta, and Mon- 

 olene have the dorsalmost and ventralmost prin- 

 cipal caudal fin rays associated with the neural and 

 haemal spines of the penultimate vertebra and 

 have a count of 1-3-5-4-3-1. In these genera the 

 left side pelvic fin base is on the median line and 

 its origin is slightly anterior to the cleithral tip 

 and to the origin of the right side base. 



In Bothus and Chascanopsettathe count of prin- 

 cipal caudal fin rays associated with the caudal 

 elements is 1 11 3-4^1, starting at the neural 

 spine and ending at the haemal spine of the pe- 

 nultimate vertebra. In Bothus and Chascanopsetta 

 the left side pelvic fin base is on the median line 

 and its origin is on the urohyal, on the right side 

 the base is short, above the median line, and its 

 origin is behind the cleithrum. 



The number of principal caudal fin rays asso- 

 ciated with caudal elements shows some variation, 

 because a fin ray may be supported in part by two 

 elements, such as hypurals, epurals, or neural or 

 haemal spines. 



LARVAL BOTHID FLATFISH AND SPOTFIN FLOUNDER 



267 



