460 Bashford Dean Memorial Volume 



specimen is certainly large. In specimen No. II (Text-figure 103b) the ventricle (v.) is 

 partially distended with blood. Its si?e equals that of No. II but its form is quite different, 

 more nearly resembling that of the human ventricles. The conus (co.) is so long that 

 proximal and distal halves, when at rest, are bent almost at right angles to each other 

 in order to find room within the pericardial cavity. In specimen No. I the proportions 

 are much the same as in No. Ill, but the ventricle, which is empty, is kidneyshaped 

 with its long axis extending transversely and its lesser curvature facing anteriorly. In 

 the undisturbed condition, the left half of the ventricle was folded dorsal to the right 

 half. In this condition, when viewed from the ventral aspect, the ventricle of No. I 

 has much the same appearance as in Giinther's figure. Thus in my three specimens, even 

 after allowing for differences due to expansion and contraction of its chambers, the form 

 of the heart as viewed from the ventral aspect varies considerably, but the ventricles 

 are uniformly larger than those shown in Carman's and Giinther's figures. 



In my three specimens, the sinus venosus {s.v. in Text'figure 103a) and the common 

 cardinal veins or ducts of Cuvier (c.c.) are of the usual elasmobranch type, but seem rather 

 large. Of the mass of spongy tissue in the posterior pericardial wall, mentioned by 

 Garman, I can find no trace. 



Concerning the valves of the conus (bulbus) arteriosus in the specimen illus' 

 trated by my Text'figure 101b, Carman (1885.2, p. 18) writes: "The bulbus contains 

 six rows of valves, or seven if we count the single valve nearest the ventricle as a row. 

 Two or three of the posterior series have chordae tendineae." Giinther's (1887, p. 4) 

 description of the conus arteriosus in his specimen follows : 



The conus arteriosus (Figs. 7 and 8) [my Text-figure 102] is of considerable length, 

 sHghtly bent towards the right, and of nearly the same diameter throughout. No special valve 

 separates it from the ventricle. I find the valves much more regularly arranged than would 

 appear from the figure given by Garman. They form three longitudinal and six transverse 

 rows (Fig. 8). The largest are those of the distal transverse row, placed close to the end of the 

 conus, and somewhat more distant from the next row than the five other rows are from each 

 other. The next largest valves are those of the proximal row, those of the second and third 

 being smaller, and those of the fourth still smaller, with only partially free anterior margins; 

 the valves of the fifth row are quite rudimentary, and two of them merely indicated as raised 

 papillae, which are confluent with those of the fourth row. Finally, a fourth intermediate 

 longitudinal series is indicated by two minute valves, belonging to the first and second 

 transverse rows. The larger valves are provided with tendinous chordae. 



The valves of the conus in my three specimens are regularly arranged in transverse 

 rows, but the arrangement in longitudinal rows is not always perfect. In specimen No. 

 Ill the valves are the largest, but this may be due to the fact that they are best preserved. 

 In this specimen there are five transverse rows, with a space of double the usual extent 

 between the fourth and fifth rows counting from the proximal end of the conus. The 

 valves of the distal row are much the largest, as in Carman's specimen; the valves of the 

 two proximal rows rank next in si2;e. The numbers of valves in each row, reckoning from 

 the proximal end of the conus, are 3, 4, 4, 5, and 3 respectively. In specimen No. II there 



