5 2 o Memoir Sears Foundation for Marine Research 



nature proven by openings through which spinal nerves emerge." Midanterior part of 

 vertebral column bearing neural arches with processes as well as haemal arches, these 

 dwindling away toward head, and also rearward from level of pelvic girdle. 



Axial skeleton of clasper articulated to inner edge of basal cartilage of pelvic fin; 

 two short basal cartilages (the first with a small cartilaginous element on inner side) and 

 a long slender terminal cartilage, either simple or with two slender rods articulated to 

 its basal part in those in which clasper is branched. Prepelvic tenaculum supported by 

 a single short blade-shaped cartilage, or by two (thought to represent a modification 

 of anterior edge of pelvic fin), articulated to pubic part of pelvis. Frontal tenaculum 

 supported by a short club-shaped cartilage, articulated to front of cranium, above and 

 in front of orbits; its tip armed with sharp recurved thorns. 



Size. The chimaeroids range in length from about 600 to 2,000 mm at maturity 

 (24 to 79 in.), with females rather larger and stouter in form than males. -^ 



Development. Fertilization is internal and is effected by the pelvic claspers, as it is 

 among all modern elasmobranchs. The act of pairing has not been observed. "By 

 indirect evidence, however, the mode of copulation appears to be distinctly shark-like. 

 The accessory claspers, i. e., the male's frontal spine and anterior appendage of the 

 pelvic fin are evidently of use in securing the female. "^^ All of the chimaeroids are 

 oviparous, depositing eggs that are astonishingly large for the size of the parent fish. 

 They are enclosed in brown horny capsules that are elliptical, spindle-shaped, or tadpole- 

 shaped, often with wide lateral longitudinal flanges or narrower median-longitudinal 

 keels, and are of curious and characteristic shapes, suggesting in their appearance 

 the fronds of some large brown alga.^* It is not known whether the embryo case has 

 openings when first laid. But soon either one pair of longitudinal slits or 45-200 pairs 

 of pores open along the margin of its posterior extension in the angles with the lateral 

 flianges. Also, a pair of so-called opercular slits open along the edges of its anterior 

 prolongation; these slits are on the side opposite to the posterior slits or opposite to 

 the pores (if these are confined to one side only), their edges either separate or inter- 

 locking so as to form a sort of grating, allowing water to enter. It is by fracturing the 

 shell crosswise, between the anterior ends of these opercular slits, that the embryo 

 escapes from the egg capsule. 



The union of the male and female sex cells takes place in the uppermost portion 

 of the oviduct, and the egg is in an early stage of cleavage when it is laid. Two eggs are 

 laid simultaneously, one from each oviduct, and a pair of capsules is often carried by a 

 female for some hours, or perhaps for days, each protruding for the greater part of its 

 length. But the actual process of deposition did not take more than ten minutes in one 



21. The anterior part of the vertebral column shows more obvious signs of segmentation in some of the fossil chima- 

 eroids. 



22. According to Dean (Chimaeroid Fishes, Publ. Carneg. Instn., 32, 1906; 13), females are about '/jj longer and '/t 

 heavier than males. 



23. Dean, Chimaeroid Fishes, Publ. Carneg. Instn., 32, 1906: 23. 



24. The following summary of development of chimaeroids is based on Dean's (Chimaeroid Fishes, Publ. Carneg. 

 Instn., 32, 1906: 48-114) account of the Californian Hydrolagus colliei and on other available sources. We have no 

 first-hand observation to contribute. 



