IIKKHINC-KISIIKS. 



947 



ciirtilajriiious fishes, representing different stages oF re- 

 (luitiiin. I'xiA.s" followed the same method with tlie 

 Tek'osts, showing that in l!iitiriiiiis then' is n <iistinct 

 rudiment of a (cii/iis <irterios/is, with transversely 

 striped muscles and t\vo rows of valvules, and that in 

 Osteot/lossiini — now the type of a separate family of 

 hard-scaled fishes whicii in otlier respects come near to 

 the Herrings — and X<itoj)tenis — belonging to a family 

 also nearly r(dated to the Herrings, l)ut with sc-alv 

 head and without o\iducts — the said rudiment is con- 

 siderably smaller and possesses only one row of val- 

 vules, answering to the front row in the ])revious fishes. 

 In the true Herrings the rudiment has almost entireh' 

 disappeared, and is replaced merelv by a layer of con- 

 nective tissue, without striped muscles; and tliis, as 

 we have already mentioned, is the t^pieal condition 

 in the Teleosts. 



The essential resemblances between the skeleton 

 of the Herrings and that of the Salmons were remarked 

 by L. Agassiz. Hut in the former the skeleton is, as 

 a rule, more firmly ossified, and shows some remark- 

 able peculiarities in systematic and morphological re- 

 spects. 



From a comparison between the skeleton of a Ven- 

 dace and that of a common Herring, it appears that 

 the same looseness prevails in the union of tlie lateral 

 parts both of tjie neural arches belonging to most of 

 the antei'ior abdominal vertebra' and the luemal arches 

 of the posterior abdominal vertebrte. The latter are 

 indeed closed throughout a considerable part of the 

 trunk, an osseous bridge joining the right shaft of the 

 arch to the left; but lower down the shafts again se- 

 parate, and the I'ibs are attached to each part of these 

 divided haemal spines. The vertebra? of the Herring 

 are further marked — as anyone who has eaten a Her- 

 ring knows — by the number of scleral bones deve- 

 loped in the tendinous walls (aponeurotic septa) between 

 the transverse divisions (myocommata) of the great 

 lateral muscles. A ])erfect abdominal vertebra (fig. 236) 

 has no less than three pairs of such bones, the first 

 («a = epineural bones) attached to the base of the neural 

 arch or at the limit between that arch and the body 

 of the vertebra, the second (pa = epicentral bones) to 

 the body of the vertebra, and the third (phi ^epipjeural 

 bones) to the base (jf the ribs or at their insertion. In 



the Safmonoids we find only one or two pairs of these 

 scleral bones, the uppei-most alone or in association with 

 tlie lowest. In most ('lupcoid forms the lower extre- 

 mities of the I'ilfs in general arc; applied to the innei- 

 surface of osseous growths from tlie skin, to whicli they 

 are, however, but loosely united. These growths belong, 

 as we have seen above in the case of the Sternopty- 

 I'lioids, to tlie median scak>s of the carinated ventral mar- 

 gin, the so-calleil \entral plates, with their spiniform 

 processes in a backwartl dii-ection (dh). 



In the Herring too a great part of the chondro- 

 cranium is continuous. The long frontal bones (fig. 237, 

 fr) send out obli(|U(!l\' backwards and downwards, on 

 each side behind the oriiits, a large process, whicli runs 

 into the squamosal bone (squ and ffos in the figure, oft 

 ■pteroticum), while the frontal bone itself behind touches 

 the parietal bone (par). Between the said three bones 

 on each side of the head flic ci'anial wall is pierced bv 



N-/-- 



Fig. 2.S6. Alulmiiiii;]! verlelira of a Herring. After Beandt and Rat- 

 ZEBURG. ns, upper spinal process (neural spine); n, upper (neural) 

 arch; c, corpus; p, transverse process; pi, rib; «a, upper extracostnl; 

 pa, middle extracostal; pla, lower extracostal; dh, spiniferous plale 

 at the ventral margin. 



the large and oblong temporal aperture (ap)'' charac- 

 teristic of the Herrings. This aperture lies in front of 

 the mastoid groove (temporal cavity), which is rather 

 large in these fishes as well as in the Salmons and Carps, 

 its bottom being composed of the squamosal bone, car- 

 tilage, and the mastoid bone (mt in the figure, os epio- 

 ticKiii), while its walls belong ])artlv to these bones, 

 partly to the lateral portions of the squamosal part of 

 the occipital bone (ncs). It is besides furnished with a 

 roof formed bj- a backward process from the parietal 

 bone (par), meeting a forward process fi'ora the mastoid 

 bone (mt). The greater part of the roof of the cranial 

 cavitv has lost its cartiia<!;e in the Herrino-, onh' a lon- 



° Vid. Meddel. Natiirh. For. Kblivn, 1879 — 80, p. .^.=S:^. 



' The temporal aperture sometimes occurs, it is true, in the Salmou (cf. Bbucii, Osteol. Rheinlachs, tab. IV, tig. .3, between and z/), and 

 appears in the Smelt as a vestige of the great frontal fontanel in the cartilaginous cranium of young fishes. But it is tlicre covered by the frontal bone. 



