Introduction.

Having investigated Squatina squatina, one of us (B. J. M.) began, in England, to study the vascular system in various species of Raja. In New Zealand a start was made also on the dissection of the highly specialised Blind Numb Fish Typhlonarke aysoni, and the work was then taken over by M. L. P., who is responsible for the drawings and descriptions in this paper, and most of the dissections upon which they are based. The species of ray whose vascular system has been most fully described is R. nasuta, studied by T. J. Parker in this department towards the end of last century. Dissections were made of this species as a typical ray, and single specimens of the Stingray, Bathytoshia brevicaudata, and the Electric Ray Notastrape fairchildi were also dissected. The names used here are those given by Whitley (1940). Among the specimens of Typhlonarke dissected, some appeared to differ externally from T. aysoni and probably belong to another species, but no differences in the vascular system were observed.

The order Selachii is divided by Goodrich (1930) as follows: Grou p 1. Notidani.

Detailed studies of Selachian vascular systems are not very numerous, but members of the Notidani have been described by Daniel (1928), of the Scylloidei by Parker (1886), O'Donoghue (1914), and Marples (1936, 1), and of the Squaliformes by O'Donoghue (1928). Marples (1936, 2) described the vascular system of Squatina and gave reasons for its removal from the Rajiformes. No complete description of members of the Rajiform groups appears to exist, the most complete being that of R. nasuta by Parker (1884), while the posterior region of R. erinacea was described by Rand and Ulrich (1905) and Daniel (1928) gave certain details of Dasyatis dipterura, a stingray belonging to the Centrobatoidei. The present paper is an attempt to add to our knowledge of the vascular system of the Rajiformes, but a great deal of interesting work remains to be done when material is available, especially among

the stingrays. It may be mentioned that Goodrich (1909) suggests a connection between the Rhinobatidae, Pristidae and Rajidae, but a separate origin from the primitive Rajiform stock for the Torpedinidae, Trygonidae and Myliobatidae, with the Torpedinidae nearest to the Rajidae.

Typhlonarke has such a peculiarly modified skeleton that a brief description is desirable and the general disposition of the parts is shown in Fig. 1. It is oval in shape, with a very abbreviated tail and small mouth. The pectoral fins arise very far back and the pectoral and pelvic girdles overlap considerably. Between the pectoral fins and the anterior part of the body lie the large electric organs. Goodrich (1909) states that in the Torpedinidae the two halves of the pectoral girdle are not firmly fused together, but this is not true of Typhlonarke.

Figure 1.—Diagram showing the structure of Typhlonarke. (For explanation of letters see end of paper.)