OCR Text |
Show 34 PROF. T. J. PARKER ON CARCHARODON RONDELETII. [Jan. 18, c. The Skeleton of the Fins.-In the shoulder-girdle I have nothing to add to Haswell's description. The pectoral fin of specimen A exhibits a concrescence of the proximal ends of the mesopterygial rays not shown in Haswell's figure. The intercalary pieces between the distal ends of many of the rays, referred to by Haswell, are evidently due to longitudinal division of the rays, one of which, in the specimen referred to, was distinctly bifurcated. The pelvic girdle and fin are not figured by Haswell : I therefore give a figure of those of the male specimen A (Plate V. fig. 9). Haswell states that the outer extremity of the pelvic cartilage (pu) " is produced into a process with which no fewer than six rays articulate." In my specimen this process is apparently represented by a separate cartilage (a), which seems to be formed by the concrescence of the anterior rays, and to be serially homologous with the propterygium of the pectoral fin. The first dorsal fin differs only in detail from that described and figured by Haswell, who says of the second dorsal and ventral (so-called anal) fins, that they " are very small, and consist of a few irregular rays without basal plates." I find, on the contrary, that both these fins (Plate V. fig. 10, and Plate VI. fig. 15) and especially the ventral (fig. 10) are quite typical examples of the concrescence of pterygiophores (radial cartilages) to form a basipterygium. 4. Alimentary Organs. The stomach (specimen C) consists of a wide cardiac (Plate VI. fig. 16, card.st.) and a narrow tubular pyloric (pyl.st.) division. The cardiac division is about 115 cm. long and 75 cm. wide; the pyloric division 104 cm. long by 5 cm. wide. On the right side of the stomach, near its oesophageal end, are two blind pouches (x.). The intestine (int.) is 109 cm. long from the pylorus to the origin of the rectal gland, and 26 cm. in diameter. The spiral valve is regularly disposed, makes 48 turns, and is slightly narrower than the semi-diameter of the gut, so that a narrow central passage is left, as in Alopecias and in some specimens of Raia \ The rectal gland (rct.gl.) is 30 cm. long by 3'5 cm. in diameter. The cloaca (fig. 17) is comparatively small, and is divided by a horizontal fold into two chambers, an outer (cl2) receiving the oviducts (ovd.ap.), and an inner (cl1) receiving the rectum (ret) and the urinary duct (ur.ap.). The liver consists of two immense lobes, which fill all the ventral region of the abdominal cavity. In specimen C the gland was too much decomposed for its form and size to be made out, but in D (5 metres long) each lobe was about 135 cm. long, by 102 cm. wide, and fully 30 cm. thick. A gall-bladder is present. The spleen and pancreas have tbe usual characters ; tbe pancreas (Plate VI. fig. 16, pan.) consisting of a small ventral and a large 1 T. J. Parker, " On the Intestinal Spiral Valves in the Genus Eaia," Trans. Zool. Soc. vol. xi. p. 50. |