. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Ceratostethus—Osteology and Structural Novelties • Roberts 403 maxillary processes never diverge from each other. Submaxillary process of maxillary articu- lated to prevomer by submaxillary bone (developed in place of the usual submaxil- lary meniscus). Submaxillary bone forms ja meniscus with submaxillary process of .maxillary and with anterior end of pre- v^omer. When mouth is closed, submaxillary bone lies with its upper end at an angle of ibout 15 or 20 degrees anterior to a vertical; when mouth is protracted, rot
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Ceratostethus—Osteology and Structural Novelties • Roberts 403 maxillary processes never diverge from each other. Submaxillary process of maxillary articu- lated to prevomer by submaxillary bone (developed in place of the usual submaxil- lary meniscus). Submaxillary bone forms ja meniscus with submaxillary process of .maxillary and with anterior end of pre- v^omer. When mouth is closed, submaxillary bone lies with its upper end at an angle of ibout 15 or 20 degrees anterior to a vertical; when mouth is protracted, rotation Df maxillary depresses upper end of sub- naxillary, which finally lies at an angle of ibout 45 degrees from vertical with mouth ully protracted. The curved, ventrally di- rected internal hooks of the maxillaries are igamentously attached to a median ossified element or rostral bone lying ventrally to iscending processes of premaxillaries. (This slement evidently is represented by a •QStral cartilage in atherinoids; it is similar n position, but not in movement, to the 3yprinoid kinethmoid.) With mouth closed, interior tip of rostral is horizontal with the interior tips of the nasal bones and an- erior margins of maxillaries; when mouth s fully protracted, it moves forward ap- proximately 50 percent of its length. Above :he rostral, in thickened connective tissue attaching it to ascending premaxillary proc- esses and internal hooks of maxillary, lies a lair of small bones or pararostrals. Tliese ire evidently equivalent to accessory rostral :;artilages of some atherinoids. Movement )f pararostrals equal to movement of ostral. Lower jaws similar in form to those in itherinoids: dentaries with very large cor- )nary process, and with ventrally opened lange forming a trough for mandib- ilar segment of cephalic laterosensory iystem. Maxillomandibulary ligament, link- ng tips of the ventral limb of maxillary and ,)remaxillary to dentary, is similar to that In atherinoids (
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