No. I.] MORPHOLOGY OF CLADOSELACHE. rat 
caudad end not protruding; radialia, with little trace of 
jointed structure, extending from body-wall to fin tip, 
tending to concentrate and fuse in the anterior fin margin.} 
Claspers absent. A circum-orbital ring of derm plates. 
Evidence of loose integumentary gill flaps. Myocommata 
often preserved in fossils. 
SUBORDER I, CLADOSELACHII. 
Membrane bones together with neural and haemal spines 
lacking. Suspensorium probably short and down-turned. 
In paired fins concrescence of anterior elements giving rise 
to specialization of radialia, and tending to rotate entad the 
fused basalia; the anterior fin region therefore becoming the 
more modified, tending to mask its structural characters: in 
pectoral the specialization of anterior radials producing a bow- 
like fin margin; in ventral the foremost basalia as yet unfused: 
the fins’ body angle, anterior and posterior (horizontal), 
rounded by dermal investiture, the remnant perhaps of the 
continuous lateral fold. Circum-orbital ring of many derm 
plates. 
FAMILY CLADOSELACHIDAE. 
Body fusiform, presenting a horizontal dermal keel at the 
base of the tail. Fins bluntly lobate: in pectoral the posterior 
radials often bifurcate. Teeth cladodont. Anal and dorsal 
probably small, lacking in fin spine (?). Circum-orbital derm 
plates quadrangular and in concentric rows. 
GENUS CLADOSELACHE. 
Body bluntly fusiform. Teeth cladodont, p. 106. Shagreen 
varying in body regions. In pectoral delicate (dermal) rays 
between radialia, radialia in character as described p. 92. 
Tail, with basal supports arranged as shown p. 98, exhibiting 
fine (dermal) ray structure in place of hypurals of upper lobe. 
The Acanthodians would then follow as presented by Smith 
Woodward, but regarded as a sub-order. 
1JIn the order Selachii on the other hand, the concentration, splitting and 
fusing of the radialia is at the posterior (distal) fin end, consequent of the 
protrusion of the tip of the basalia in this region. 
