NILS ROSEN, STUDIES ON THE PLECTOGNATHS. / 



There is some difference in tbe statements given by the above 

 named authors as to the number of the semilunar valves. 

 According to Cxjvier there are four valves between the 

 auricle und the ventricle, but Meckel says that three is the 

 ordinary number. Stannius and Wahlgren found four 

 valves, while Harting states their number to be five (p. 18): 

 »a Forifice qui conduit de Toreillette au ventricule, il y a 

 d'abord deux grandes valvules semilunaires, placées å peu 

 prés dans Faxe longitudinal de Torgane. Dans la direction 

 opposée, rintervalle du coté droit entré les deux grandes 

 valvules est occupé par la valvulve h, Tintervalle gauche par 

 les deux valvules c et d, dont la derniére est tres petite. 

 La nombre total des valvules en cet endroit est par consé- 

 quent de cinq.» 



I have not had any oppurtunity to examine the heart 

 of Orthagoriscus myself, but as most writers have stated the 

 valves to be four, it seems most probable to me, that this 

 is the ordinary number and that the occurrence of only three 

 or of so many as five must be considered as individual varia- 

 tion, due to a coalescence or splitting of the normal valves. 

 I think, moreover, the fact that in the specimen examined 

 by Harting the fifth valve is much smaller than the other 

 and irregularly placed, speaks for this view. In any case it 

 is of interest to note that the number of valves in question 

 is greater in Orthagoriscus, than in any other Plectognath. 

 The number of the valves in conus arteriosus is also greater 

 than the usiial one in the Plectognaths. There are four of 

 them, two larger and two smaller, but they are all arranged 

 on the same transverse plan. 



With the present insufficient knowledge of the heart of 

 the Teleostean fishes I think it is almost impossible to make 

 any remarks about the heart of the Plectognaths from a 

 phylogenetical point of view. There are, however, a few 

 facts already stated to which attention ought to be drawn in 

 this respect. The number of valves between the auricle and 

 the ventricle as well as in the conus arteriosus is, as men- 

 tioned above, greater in Orthagoriscus than in other Plecto- 

 gnaths. As to the atrio-ventricular valves such a great num- 

 ber is, as far as I know, not found in any other Teleost, 

 but in the Ganoids. To estimate the phylogenetical value 

 of the above named fact is, of course, a ratlier delicate 



