_Batrachoseps pacificus_ is a larger species than _Batrachoseps attenuatus_. Its general appearance, owing to the greater broadness of head and body, is very suggestive of the various species of _Plethodon_. This resemblance is carried further in one specimen by the presence of five digits on one hind foot. Structurally, however, the species is a true _Batrachoseps_; that is to say, the tongue is adherent anteriorly, the digits are normally 4-4, the premaxillary is single, and there is a large parietal fontanelle. _Diagnosis._--Costal grooves usually seventeen (rarely sixteen or eighteen); head much broader than body; color yellowish brown above, white or yellow below. _Description._--General form elongate, slender; body cylindric or somewhat flattened; tail conical, a little longer than head and body; head depressed, rather broad, nearly circular in outline from above; snout rounded or truncate from above, truncate and high in profile; eyes large and rather prominent, separated anteriorly by about the length of the orbital slit; nostrils small, near corners of snout, separated by a little more than their distance from orbits; a very indistinct subnasal groove, not extending to margin of lip; upper jaw overhanging lower; line of lip nearly straight to below eye, then deflected downward; palatine teeth in 2 nearly straight very oblique series which nearly meet on the median line posteriorly and anteriorly do not extend to the internal nares; parasphenoid teeth separated by a narrow space posteriorly but confluent anteriorly, extending nearly to the palatine series; internal nares rather small, in front of the anterior ends of the series of palatine teeth; tongue large, oval, not emarginate, attached along the median line, free laterally and posteriorly; neck not distinct from body, with several vertical and 2 or 3 longitudinal grooves; gular fold well marked, continued forward on side of neck to eye; 1 or 2 indistinct grooves anterior to gular fold; costal grooves between limbs usually 17, occasionally 16 or 18,[2] continued nearly to midline on back and belly; limbs short, weak, each with 4 digits; digits with rounded knob-like ends, inner digit short, rudimental, others well-developed, second and fourth nearly equal, third longest, web small or absent; tail more slender than body, with well-marked lateral grooves; a more or less indistinct dorsal longitudinal groove, most distinct on neck and pelvic region; skin smooth with minute pits; adpressed limbs widely separated. [Footnote 2: In fifty specimens the costal grooves are 17 in forty, 16 in six, and 18 in four.]