OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 353 



It is indisputible that only the genera included in Matsumoto's 

 subfamily Ophiolepidinae — that is, the genera Ophiomisidium, 

 Ophiolepis, Ophiozona, etc. — possess mouth pores opening into the 

 mouth slits in the strict sense of the word, and these pores, situated 

 more or less deeply, are not visible externally when the ophiuran 

 is viewed on the ventral surface. But this is not the case in the 

 subfamily Ophiomastinae in the different representatives of which 

 these pores, whatever may be their external appearance and how- 

 ever near they may approach the mouth slits, never, strictly speak- 

 ing, open into the mouth. Let us consider the ventral surface of 

 forms such as Stegophiura stereo, (pi. 83, fig. 2), S. sladeni (pi. 83, 

 fig. 4), S. sterilis (pi. 83, fig. 9), Ophiura sarsii (pi. 84, figs. 10, 11), 

 O. flagellata (pi. 86, figs. 1, 2), in order to take as illustrations only 

 species of which photographs are included here, and we shall see 

 that these pores are always very much developed, that they are more 

 or less elongated, and that they very often have their proximal ex- 

 tremity broadened; certain of them appear to open entirely into 

 the mouth slits, and others, which are somewhat more distant from 

 it, appear not to open into it. Actually these pores do not really 

 open into the mouth, and if we believe that we see them opening 

 thus this is due to a superficial appearance. The opening of these 

 pores is on the same plane as the ventral surface of the correspond- 

 ing oral plates — that is, on a plane slightly lower than that of the 

 mouth slit — and it is always separated from the latter by an inter- 

 val, very slight, it is true, though actually existing. Furthermore, 

 a careful examination often permits the determination of the pres- 

 ence of one or two mouth papillae which affirm, in a way, this sepa- 

 ration; in default of mouth papillae, the border of the oral plate 

 itself forms a sort of ceiling to the tentacle pore and separates it 

 from the mouth. 



In the species which I have just mentioned and in many others, 

 the mouth pores in reality open like the following pores on the ven- 

 tral surface of the arms, and it is not correct to say that these pores 

 open into the mouth slits; it is preferable to say that these pores, 

 which are elongated and much developed, often broadened and even 

 gaping from the side of the mouth slits, have their proximal ex- 

 tremity rather close to these slits and thus appear to open into them. 



If the arrangement of these pores be compared with that which is 

 noticed in species such as Ophiura imbecillis, Homalophiura, in- 

 ornata, H. nana, Amphiophiura undata, A. abcissa, etc., a consider- 

 able difference will be found. In these latter species the pores are 

 small, narrow, always distant from the mouth slits, and their proxi- 

 mal end is closed like their distal. In speaking of these pores we 

 say — H. L. Clark and myself — that they do not open into the mouth ; 

 that is not sufficient to distinguish them from the pores of species 

 55269— 22— Bull. 100 23 



