The Book of Household Management by Mrs. Beeton

_osseous_ and the _cartilaginous_, yet the distinction is not very precise; for the first have a great deal of cartilage, and the second, at any rate, a portion of calcareous matter in their bones. It may, therefore, be said that the bones of fishes form a kind of intermediate substance between true bones and cartilages. The backbone extends through the whole length of the body, and consists of vertebrae, strong and thick towards the head, but weaker and more slender as it approaches the tail. Each species has a determinate number of vertebrae, which are increased in size in proportion with the body. The ribs are attached to the processes of the vertebrae, and inclose the breast and abdomen. Some kinds, as the rays, have no ribs; whilst others, as the sturgeon and eel, have very short ones. Between the pointed processes of the vertebrae are situated the bones which support the dorsal (back) and the anal (below the tail) fins, which are connected with the processes by a ligament. At the breast are the sternum or breastbone, clavicles or collar-bones, and the scapulae or shoulder-blades, on which the pectoral or breast fins are placed. The bones which support the ventral or belly fins are called the _ossa pelvis_. Besides these principal bones, there are often other smaller ones, placed between the muscles to assist their motion.