236 



Mr. E. J. Bles. On the Openings in the 



Table II. 



A. Elasmobranchs with nephrostomes when adult. 



(1) Abdominal pores absent. 



Cestraciontidae. Cestracion philippi, Lacep. 

 Rhinidse. Rhina squatina, L. 



(2) Abdominal pores absent until full-grown. (Whether they are then con- 



stantly present is not known.) 

 Scylliidae. Scyllium stellar e, L. 



Pristiurus melanostomus, Bonap. 



(3) Abdominal pores appear late (when sexually mature) and may be absent. 



Scylliidae. Scyllium canicula, L. 

 Spinacidse. Spinax niger, Bonap. 



(4) Abdominal pores appear early and are constantly present. 



Spinacidse. Acanthias vulgaris, Eisso. 

 Symnus UcMa, Cuv. 



B. Elasmobranchs without nephrostomes when adult. 



(5) Abdominal pores always present. 



Selachoidei. Carchariidae. CarcJiarias glaucus, L. G-aleus canis> 

 Bonap., Zygcena malleus, Risso, Mustelus 

 vulgaris, M. and H., M. Icevis, Bisso,, 

 Triads semifasciata, Grirard. 

 Lamnidse. Lamna cornubica, G-m. 

 Batoidei. Rhinobatidae. RMnchobatus djeddensis, Forsk. 



Rhinobatus granulatus, Cuv. 

 Torpedinidae. Torpedo narce, Risso, T. marmorata, Risso,. 



Hypnos subnigrum, Dum., Narcine bra- 

 siliensis, Olf., Raja clavata, L., R. macu- 

 lata, Montag., R. blanda, Holt and Cal- 

 derwood, R. punctata, Risso, R. miraletus y 

 L., R. batis, L., R. marginata, Lacep. 

 Trygonidae. Trygon brucco, Bonap. 

 T. pastinaca, L. 

 Myliobatidae. Myliobatis maculata, Grray, 

 Myliobatis sp. 



The most obvious of the facts brought into prominence by the 

 above tables are the following: — 



1. The Elasmobranch fishes when adult have a peritoneal cavity 



which in every known instance communicates with the 

 exterior. 



2. This communication-is established in several ways : — 



(a) Through nephrostomes and urinary canals ; 



(b) More directly, through abdominal pores ; but 



(c) • Both communications may exist together in the same 



individual. 



3. Disregarding for the moment the eight species which, roughly 



speaking, possess both sets of openings, there remain twenty- 

 eight species in which a correlation of an alternative nature 



